CN102904549B - Schmitt trigger circuit - Google Patents
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- CN102904549B CN102904549B CN201210334692.4A CN201210334692A CN102904549B CN 102904549 B CN102904549 B CN 102904549B CN 201210334692 A CN201210334692 A CN 201210334692A CN 102904549 B CN102904549 B CN 102904549B
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Abstract
The invention discloses a Schmitt trigger circuit which comprises a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a first transistor, a second transistor, a third transistor and a fourth transistor, wherein the first transistor, the second transistor, the third transistor are NPN type transistors, and the fourth transistor is a PNP type transistor; and a positive feedback circuit composed of the first resistor and the second resistor, a in-phase amplifier circuit composed of the first transistor, the third resistor, the fourth resistor and the fourth transistor and a in-phase amplifier circuit composed of the second transistor, the fifth resistor and the third transistor are parallelly connected, and when the input trigger signals are positive levels, the positive levels are amplified through two levels of short transistors and then fed back to an input end in a positive mode to obtain performance of the Schmitt trigger. The Schmitt trigger circuit adopts the two-level bipolar transistor for amplifying, the delay time is short, locking effect does not exist, trigger voltage sensitivity consistency is good, and the range of a working voltage of the circuit is wide.
Description
Technical field
The present invention relates to digital circuit, particularly Schmitt trigger circuit in digital circuit.
Background technology
For standard Schmidt trigger, when input voltage is higher than forward threshold voltage, export as high level; When input voltage is lower than negative sense threshold voltage, export as low level; When input is between positive negative sense threshold voltage, output voltage does not change, and that is exporting by high level upset is low level, or it is different for being the threshold voltage that high level is corresponding by low level upset.Only have when enough changes occur input voltage, export and just can change, therefore by this element called after trigger.This dual threshold action is called as hysteresis phenomenon (hysteretic characteristic), shows that Schmidt trigger has Memorability.So traditional theory is thought, Schmidt trigger is a kind of bistable multivibrator.
Schmidt trigger can be used as waveform shaping circuit, analog signal waveform can be shaped as the square-wave waveform that digital circuit can process, and there is hysteretic characteristic due to Schmidt trigger, so can be used for anti-interference, its application is included in open-loop configuration for anti-interference, special in switching power circuit, utilize the isolating transformer of small size that the square-wave signal that duty ratio often changes is reached next stage, when completing isolation drive, just seem very valuable, as in two-transistor forward converter circuit from the transistor close to positive supply, just need isolation drive, its frequency spectrum of the square-wave signal that duty ratio often changes is very wide, the isolating transformer of small size will complete the perfection transmission of square wave under very wide frequency, require very strict to isolating transformer.So, some technical schemes utilize a microminiature transformer, utilize its low frequency performance poor, the differential effect produced, square wave is transferred to next stage and becomes spike, recycling Schmidt trigger is reduced into square wave, and as " utilizing pulse modulation demodulation system to realize the IGBT drive circuit of the signal transmission " Figure of abstract of Chinese publication number 101640527 of having had no right, digital 2 indications are exactly this circuit.For convenience of description, here quote as Fig. 1 herein, microminiature transformer T is converted to spike the square wave on former limit, this circuit utilizes two reverser U1A and U1B to connect, add the regenerative circuit of resistance R4 and the diode D1 series connection of only working when high level, complete " burst pulse passed over by pulse transformer is reduced to control signal ".
In fact, select cmos digital circuit just can realize this function, but along with the progress of power standard, power technology, as now widely used half-bridge logical link control (LLC) resonant converter, its conversion efficiency is very high, its operating frequency often rise to 300KHz to 500KHz even more than, at this moment very harsh to the delay requirement of isolation drive, synchronous rectification driving, the time delay of CMOS one-level just has 25-50ns duration, 50-100ns duration is just had after two-stage series connection, in actual use, because operating frequency is very high, the locking-up effect of COMS circuit is easy to occur.COMS circuit is owing to inputting too large electric current, and inner electric current sharply increases, unless cut off the electricity supply, electric current is increasing always, and this effect is exactly locking-up effect.When producing locking-up effect, the internal current of COMS can reach more than 40mA, is easy to burn chip; Burn Switching Power Supply simultaneously.
CMOS due to inside be metal-oxide-semiconductor input, its input voltage sensitivity affects by the cut-in voltage of metal-oxide-semiconductor, and consistency is bad, Switching Power Supply batch production time, the bad guarantee of consistency of driving.
Certainly, the puzzlement of selecting TTL digital circuit can solve above-mentioned CMOS to bring, TTL digital circuit speed is fast, and as 74HC14, the time delay of its one-level gate circuit only has 5-10ns duration, can meet current requirement.But TTL digital circuit operating voltage is 5V, its output voltage is generally about 3.5V, drives follow-up MOS power tube or the metal-oxide-semiconductor of synchronous rectification, all there is driving voltage deficiency, common MOS power tube or the metal-oxide-semiconductor of synchronous rectification, if expect extremely low conducting internal resistance R
dS (ON), require driving voltage all at more than 7V, its output voltage of boosting drive integrated circult released as a lot of company is all at about 10V.
The Chinese publication number of having authorized is the 3rd row of [0015] section in the mandate text of " insulated dc-dc converter " of 101595630, also point this out: but be generally about 7V due to its absolute maximum rating voltage of general high-speed logic gate IC, therefore the gate drive voltage of the first switch element Q1 becomes the voltage lower than it.If the first switch element Q1 is not the MOSFET that logic level can be utilized to drive, then gate drive voltage is not enough.
Namely the burst pulse passed over by pulse transformer of TTL digital circuit composition is reduced to the circuit of control signal, one-level level shifting circuit need be added again in rear class, i.e. previously described " boosting drive integrated circult ", this grade of circuit generally also can bring time delay, and add cost, the general need of this circuit low speed about 0.80 yuan, at a high speed all more than 2 yuan.
Not only increase the complexity of circuit, because device increases, also reduce the reliability of circuitry, day by day pursuing the epoch of high power density, small size, add a slice boosting drive integrated circult and can bring very large trouble to the design of circuit board! According to synchronizing relay method, namely the link of all driving power levels, adopts identical time delay, so will add multi-disc boosting drive integrated circult or delay circuit, and will take more large circuit board area.
On textbook, also the circuit of Fig. 2 can be used to explain as the principle of Schmidt trigger, Fig. 2 realizes with the comparator or operational amplifier that access positive feedback, wherein, Vin is the signal input part of Schmitt trigger circuit, Vout is the signal output part of Schmitt trigger circuit, for this circuit, overturn the position occurred in closely, amount of hysteresis is controlled by the resistance of R2 and R4, this circuit Problems existing is, if export the driving voltage of 5V, time delay is 50nS, so to switching rate (the Slew rate of comparator or operational amplifier, also translations slew rate) require up to 10
5v/uS, this is unpractical, operational amplifier also so not good at present or voltage comparator.
On textbook, also can use the Schmidt trigger circuit based on 2 transistors shown in Fig. 3, as shown in Figure 3, resistance RC1 in path, R1, R2 sets the base voltage of transistor T2, but, this dividing potential drop path can be subject to the impact of transistor T1, if transistor T1 saturation conduction, path will provide extremely low voltage to the base stage of transistor T2 to emitter, namely when Vin input high level, transistor T1 saturation conduction, transistor T2 ends, supply voltage V+ provides high level by resistance RC2 to Vout, when high level state, output voltage is close to V+, another process in contrast, therefore, the threshold voltage overturn between two states depends on the existing state of trigger.
In Fig. 3 circuit, when the common emitter voltage of input voltage vin lower than transistor T1 and T2, T1 can not conducting.The base voltage of transistor T2 is determined by above-mentioned bleeder circuit.Due to access negative feedback (resistance RE is formed), resistance RE is arranged so that dual threshold action comes true, voltage added on common emitter must lower than the voltage that bleeder circuit obtains, so just can make transistor T2 conducting, and the output of trigger is low level state, due to the existence of resistance RE terminal voltage, output low level state is unsatisfactory; Just because of high level relies on resistance RC2 to provide, and low level relies on transistor T2 lead saturation conduction and obtain through resistance RE, and this just determines when low level state, and output voltage still can far away higher than ground wire voltage.Therefore in this case, output voltage is low not, cannot reach logic low, and this just needs booster amplifier on flip-flop circuit.
So this circuit can only demonstrate use as experimental teaching, in the Switching Power Supply of industrial circle drives, there is no actual using value.
Fig. 4 shows the basic element circuit in actual TTL digital integrated circuit: inverter (not gate).Also the function of Fig. 4 inverter can be realized with discrete component.This circuit is made up of three parts, the i.e. input stage of transistor T1 built-up circuit, transistor T3, T4 and diode D form output stage, and the intergrade to be made up of transistor T2 is as the drive circuit of output stage, the single ended signal of the base stage of transistor T2 is converted to complementary both-end output signal, to drive T3 and T4.The operation principle of the TTL inverter of Fig. 4:
(1) when being input as high level, as Vin=1.7V and above time, power supply V+ provides base current by the collector junction of Rb1 and transistor T1 to transistor T2, T3, makes T2, T3 saturation conduction, exports as low level, Vout=0.15V.Now the base voltage of transistor T1 is
Vb1=Vbc1+Vbe2+Vbe3=(0.7+0.7+0.7) V=2.1V ... formula (1)
Obviously, at this moment the emitter junction of transistor T1 is in reverse bias, and collector junction is in forward bias (base stage to a current collection very PN junction, forward conduction).Because T2 and T3 is saturated, export Vc3=0.15V, the value of the collector voltage Vc2 of transistor T2 can be estimated simultaneously:
Vc2=Vce2+Vb3=(0.15+0.7) V=0.85V ... formula (2)
Now, Vb4=Vc2=0.85V.The voltage acting on the emitter junction of transistor T4 and the series arm of diode D is Vc2-Vout=(0.85-0.15) V=0.7V, obviously, T4 and diode D is cut-off state, achieves the logical relation of inverter: when being input as high level, exports as low level.
(2) when being input as low level, as Vin=0.3V and following time, the emitter junction conducting of transistor T1, its base voltage equals input voltage vin and adds emitter junction forward voltage drop, namely
Vb1=(0.3+0.7) V=1.0V ... formula (3)
Now Vb1 acts on the collector junction of transistor T1 and the emitter junction of transistor T2, T3, is equivalent to the pressure drop of 3 diodes, needs the good conducting of 2.1V ability.The voltage of 1.0V cannot open 3 PN junctions, so transistor T2, T3 end, at this moment the base stage of transistor T4 is because the existence of resistance Rc2, and V+ provides base current by Rc2 to transistor T4, transistor T4 is in conducting state, exports high level through diode D.Output voltage is
Vout ≈ (V+)-Vbe4-V
d=(5-0.7-0.7) V=3.6V ... formula (4)
This is also the major reason of TTL digital circuit driving voltage deficiency, and certain TTL digital circuit also has its advantage, and as adopted the emitter of transistor T1 as input stage to improve operating rate, its principle is:
As shown in Figure 4, when TTL inverter input voltage Vin is by the moment of high (as 3.6V) step-down (0.3V), base voltage Vb1=(0.3+0.7) V=1.0V of transistor T1.But because transistor T2, T3 are originally saturation conduction, their base stored charge also has little time to dissipate, this is also usually said triode memory time (storage time), all there is a memory time (Storage time) in bipolarity triode, namely, when transistor base receives cut-off signals, collector current wants the time delay a bit of time just to start to decline until turn off.This moment, the emitter junction of transistor T2, T3 is still in forward bias, namely the collector voltage of transistor T1 be the base stage of transistor T2 and T3 to emitter junction voltage sum:
Vc1=Vbe2+Vbe3=(0.7+0.7) V=1.4V ... formula (5)
Now, the transmitting very 0.3V of transistor T1, base voltage is 1.0V, and collector voltage is 1.4V, namely forward bias is become in the transmitting of transistor T1, and collector junction is reverse bias, so transistor T1 is operated in amplification region, at this moment produce base current ib1, the enlarging section number of this pipe is β
1, the collector current ic1 ≈ β after amplifying
1× ib1, its direction is the collector electrode flowing to T1 from the base stage of T2, then flows to the emitter of T1, takes unnecessary stored charge away soon from the base of T2, makes transistor T2 promptly depart from saturated and enter cut-off state.The rapid cut-off of transistor T2 causes T4 conducting at once, the load being equivalent to T3 is a very little resistance, the collector current of transistor T3 is strengthened, and from the dissipation of transistor T3 collector electrode, transistor T3 reaches cut-off to unnecessary stored charge rapidly, thus accelerates State Transferring.
When TTL inverter input voltage Vin uprises the moment of (3.6V) by low (as 0.3V), there is analysis above.Can see from above-mentioned analysis, no matter be export high level, or low level, basic element circuit in TTL digital circuit---not gate, all will through 3 grades of transistor process, the time delay namely produced is 3 times of single stage transistor, for the standard application circuit shown in Fig. 1, could will output signal through 6 grades of transistor delay process, slowed down conversion speed.
In sum, existing Schmitt trigger circuit has following deficiency:
1, just have 50-100ns duration after CMOS integrated circuit two-stage series connection, locking-up effect is easy to occur, is easy to burn chip; Burn Switching Power Supply simultaneously;
2, CMOS integrated circuit input voltage sensibility consistency is bad, Switching Power Supply when producing in batches, the bad guarantee of consistency of driving;
3, the operating voltage of TTL digital integrated circuit is low, and the driving voltage of output is not enough; Level shifting circuit need be added during use;
4, available circuit needs with two not gate series connection, and inside is 6 level works, and time delay is larger.
Summary of the invention
In view of this, the present invention will solve CMOS and easily occur that locking-up effect, input voltage sensitivity consistency are bad, and the operating voltage of TTL digital integrated circuit is low, driving voltage is low, needs with two not gate series connection, inside is 6 level works, causes the large series of problems of time delay.The invention provides Schmitt trigger circuit, there is not locking-up effect, input voltage sensitivity consistency is good, and operating voltage range is wide, and delay time is short.
The object of the invention is to be achieved through the following technical solutions:
A kind of Schmitt trigger circuit, comprise the 1st resistance, the 2nd resistance, the 3rd resistance, the 4th resistance, the 5th resistance, 1st triode, the 2nd triode, the 3rd triode, the 4th triode, wherein, 1st triode, the 2nd triode, the 3rd triode are NPN type triode, 4th triode is PNP type triode, comprises 4 terminals, signal input part, signal output part, working power end, earth terminal simultaneously; Its annexation is: one end of the 1st resistance is signal input part, and the other end of the 1st resistance connects one end of the 2nd resistance, and the other end of the 1st resistance and the tie point of one end of the 2nd resistance are also connected the base stage of the 1st triode and the base stage of the 2nd triode simultaneously; The other end of the 2nd resistance is the signal output part of Schmitt trigger circuit, connects the base stage of the 3rd triode and the collector electrode of the 4th triode simultaneously; The emitter of the emitter of the 1st triode, the emitter of the 2nd triode and the 3rd triode is all connected to earth terminal, the collector electrode of the 1st triode connects the 4th resistance by the 3rd resistance, the other end of the 4th resistance connects working power end, 3rd resistance is also connected the base stage of the 4th triode with the tie point of the 4th resistance simultaneously, and the emitter of the 4th triode connects working power end; The collector electrode of the 2nd triode connects working power end by the 5th resistance, and collector electrode and the 5th ohmic connection points of the 2nd triode are connected the base stage of the 3rd triode simultaneously; 1st triode and the 2nd triode are the triode of same model.Being called for short the program is below primitive technology scheme of the present invention.
Technical scheme two: as the further improvement of above-mentioned primitive technology scheme, in primitive technology scheme, increases by the 6th resistance, and the emitter of the 4th triode connects working power end by the 6th resistance.As the further improvement of above-mentioned two kinds of technical schemes, increase the 7th resistance, the 8th resistance, the 7th resistance is gone here and there between the 1st transistor base and the tie point of the other end of the 1st resistance and one end of the 2nd resistance, between the 2nd transistor base and the tie point of the other end of the 1st resistance and one end of the 2nd resistance, go here and there the 8th resistance, other annexation is constant.
As the further improvement of above-mentioned first two technical scheme, present invention provides the method for designing of a kind of circuit or a kind of integrated circuit, 1st triode and the 2nd triode are a two collector electrode triode, and namely base stage, emitter jointly, and make the triode of two collector electrodes.
As the further improvement of technique scheme, the 5th above-mentioned resistance can be substituted with constant-current source.
Operation principle of the present invention illustrates:
Operation principle is set forth with the annexation of above-mentioned primitive technology scheme, when applying the triggering signal of positive level externally to signal input part, according to annexation, 1st triode and the 2nd triode ON, in circuit, the value of the 3rd resistance, the 4th resistance and the 5th resistance has guaranteed that the 1st triode and the 2nd triode are saturation conductions; So, the 3rd triode due to its base stage be the collector electrode of connection the 2nd triode, and at this moment the 2nd triode is saturation conduction, and the base stage of the 3rd triode is very low and end, meanwhile, because the 1st triode is saturation conduction to the voltage of emitter; 4th resistance and the 3rd resistance have electric current to flow through, at this moment, the emitter of the 4th triode connects working power end, and base stage is connected on the tie point of the 3rd resistance and the 4th resistance, therefore the 4th triode ON of positive-negative-positive, its collector electrode provides electric current to signal output part, and signal output part exports high level, this high level is applied to the base stage of the 1st triode, the 2nd triode through the 2nd resistance, maintains circuit and exports this state of high level;
This moment, if when applying the triggering signal of negative level externally to signal input part, this signal is after the 1st resistance, the 2nd electric resistance partial pressure, if voltage is less than base stage, the emitter forward conduction voltage of the 1st triode and the 2nd triode, generally at about 0.6V, so the 1st triode and cut-off of the 2nd triode, 3rd triode due to its base stage be the collector electrode of connection the 2nd triode, the base stage of the 3rd triode obtains electric current and conducting, meanwhile, because the 1st triode also synchronously ends from the 5th resistance; Whether the 4th resistance and the 3rd resistance have electric current to flow through, equally, the emitter of the 4th triode connects working power end, and base stage is connected on the tie point of the 3rd resistance and the 4th resistance, therefore the 4th triode cut-off of positive-negative-positive, its collector electrode no current exports, and the 3rd triode conducting, signal output part output low level, this low level is applied to the base stage of the 1st triode, the 2nd triode through the 2nd resistance, maintains this state of output low level of circuit;
Because the base stage of the 1st triode and the 2nd triode, emitter are in parallel, the base stage of the 4th triode and the 3rd triode is controlled respectively from its collector electrode, the signal of signal input part all only triggers through two-stage triode at every turn, one of them passage is the passage of the 2nd triode and the 3rd triode composition, and another passage is the passage of the 1st triode and the 4th triode composition.Owing to often only triggering through 2 grades of triodes, the impact that triode brings memory time, under the prerequisite of identical manufacturing process or triode, the TTL basic element circuit that in background technology, Fig. 4 is corresponding will realize Schmidt trigger, needs 6 grades, obviously, the delay time of Schmitt trigger circuit of the present invention is shorter than the circuit of prior art, and cost of the present invention is also low, and the circuit of prior art needs 2 not gate series connection, need 8 transistors altogether, and the present invention only have 4 transistors.
Based on above-mentioned principle, in primitive technology scheme, increase by the 6th resistance, the emitter of the 4th triode connects working power end by the 6th resistance; Like this, when the 1st triode saturation conduction, the 4th triode seals in the 6th resistance due to emitter to power supply, and the way of output of the 4th triode becomes constant-current source restraint-type and exports, and limits the maximum output current of the 4th triode, protects circuit and be not damaged.
Mention above, increase the 7th resistance, the 8th resistance, the 7th resistance on string in the 1st transistor base, the 8th resistance on string in the 2nd transistor base, other annexation is constant; So the base stage of the 1st triode and the 2nd triode, emitter are in parallel, be the equal of mirror image work, this consistency to triode proposes high requirement, increase by the 7th resistance, the 8th resistance mainly prevent the 1st triode, the characteristic of the 2nd triode differs to, this operation principle sealing in shunt resistance is known technology.
Substitute the 5th above-mentioned resistance with constant-current source, obviously, when operating voltage raises, the operating current of this one-level is constant, improves the operating voltage adaptability of circuit.
Compared with prior art, because this circuit employs bipolarity triode, do not use metal-oxide-semiconductor, there is not locking-up effect, and due to signal output part be control the 1st triode, the 2nd triode base stage to emitter conducting voltage, only need the voltage being greater than 0.7V, have highly sensitive, the feature that consistency is good; Owing to only having used 2 grades of circuit, compared to existing technology 6 grades, delay time has been shorter than the circuit of prior art, and namely the present invention has following beneficial effect:
The invention provides Schmitt trigger circuit, there is not locking-up effect, input voltage sensitivity consistency is good, and operating voltage range is wide, and delay time is short.
Because device is few, also lower than prior art on cost.
Accompanying drawing explanation
Fig. 1 is that the part of the open file Figure of abstract of Chinese publication number 101640527 quotes figure;
Fig. 2 is circuit theory diagrams textbook being explained the use of Schmidt trigger principle;
Fig. 3 is the circuit theory diagrams of Schmidt trigger circuit textbook using 2 transistors;
Fig. 4 is the basic element circuit in actual TTL digital integrated circuit;
Fig. 5 is the circuit theory diagrams of first embodiment of the invention;
Fig. 6 is the oscillogram of the first former limit of embodiment isolating transformer T, signal output part;
Fig. 7 is the TTL basic circuit signal input part Vin of the reality of Fig. 4, the oscillogram of signal output part Vout;
Fig. 8 is the circuit theory diagrams of second embodiment of the invention;
Fig. 9 is the circuit theory diagrams of third embodiment of the invention;
Figure 10 is the circuit theory diagrams of fourth embodiment of the invention;
Figure 11 is the circuit theory diagrams of fifth embodiment of the invention;
Figure 12 is the constant-current source schematic diagram of the first low cost;
Figure 13 is the constant-current source schematic diagram of another kind of low cost.
Embodiment
first embodiment
Fig. 5 shows the circuit theory diagrams of first embodiment of the invention; Draw circuit diagram by the annexation of primitive technology scheme of the present invention.Comprise the 1st resistance R101, the 2nd resistance R102, the 3rd resistance R103, the 4th resistance R104, the 5th resistance R105,1st triode T101, the 2nd triode T102, the 3rd triode T103, the 4th triode T104, wherein, 1st triode T101, the 2nd triode T102, the 3rd triode T103 are NPN type triode, 4th triode T104 is PNP type triode, comprise 4 terminals, signal input part Vin, signal output part Vout, working power end V+, earth terminal simultaneously; Its annexation is: one end of the 1st resistance R101 is signal input part Vin, and the other end of the 1st resistance R101 connects one end of the 2nd resistance R102, and tie point also connects the base stage of the 1st triode T101 and the base stage of the 2nd triode T101 simultaneously; The other end of the 2nd resistance R102 is the signal output part Vout of Schmitt trigger circuit, connects the collector electrode of the 3rd triode T103 and the collector electrode of the 4th triode T104 simultaneously; The emitter of the emitter of the 1st triode T101, the emitter of the 2nd triode T102 and the 3rd triode T103 is all connected to earth terminal, the collector electrode of the 1st triode T101 connects the 4th resistance R104 by the 3rd resistance R103, the other end of the 4th resistance R104 connects working power end V+, 3rd resistance R103 is also connected the base stage of the 4th triode T104 with the tie point of the 4th resistance R104 simultaneously, and the emitter of the 4th triode T104 connects working power end V+; The collector electrode of the 2nd triode T102 connects working power end V+ by the 5th resistance R105, and collector electrode and the 5th resistance R105 tie point of the 2nd triode T102 are connected the base stage of the 3rd triode T103 simultaneously;
Wherein design parameter is: the 1st resistance R101 is 3.3K, the 2nd resistance R102 is 10K, the 3rd resistance R103 is 1K, the 4th resistance R104 is 300 Ω, the 5th resistance R105 is 2.2K, 1st triode T101, the 2nd triode T102, the 3rd triode T103 are 2N3904, and the 4th triode T104 is the supporting 2N3906 with 2N3904.Working power end V+ is 5V direct current.
The isolating transformer T of input adopts the magnetic core of PC95 material, the magnet ring of external diameter 4.3mm, internal orifice dimension 1.5mm, high 1.8mm; Former limit coiling 5 circle, secondary coiling 1 circle provides spike triggering signal, signal source is that the 33210A function/arbitrary waveform generator of Agilent company is as signal source, operating frequency is 1MHz, export as 5V peak-to-peak value, through the matching network in 50 Europe, be added to the former limit of isolating transformer T through the capacitance electric capacity that is 103 (0.01uF).The oscilloscope observed is the MSO2014 of Tektronix, and 1 passage observes the former side wave shape of isolating transformer T, and the signal output part Vout that 2 passages are connected on Fig. 5 observes, and the waveform obtained as shown in Figure 6.Can find out, signal is 182.7nS (in figure 6 center-right side, bottom) by time delay.
Seal in ammeter in the supply, the operating current of the first embodiment is 4.06mA.
In order to contrast, we have employed the basic element circuit in the TTL digital integrated circuit of the reality of Fig. 4, its function is realized with discrete component, wherein triode T1 to T4 all adopts the 2N3904 of same producer same model, resistance value is as indicated in figure, Rb1 is 4K, Rc2 is 1.6K, Re3 is 1K, Rc4 is 130 Ω, owing to being single-stage not circuit, signal cannot be realized keep, so the Vin that the 33210A signal source of Agilent company is directly connected on Fig. 4 through the matching network through 50 Europe over the ground between, the oscilloscope observed adopts same above-mentioned equipment, 1 passage observes Vin waveform, the signal output part Vout that 2 passages are connected on Fig. 4 observes, the waveform obtained as shown in Figure 7.Because this is a not gate, signal is reversed, and can find out, signal is 320nS (after upper right portion measures the square fenestella last column △ symbol of display in the figure 7) by time delay.
Can see from Fig. 7, the feature of this basic inverter (not gate) of Fig. 4 circuit is: when input signal is in rising edge, time delay is minimum simultaneously, and actual measurement only has 28nS; When input signal is in trailing edge, time delay is comparatively large, surveys as 320nS; So when the circuit connected in series such with two Fig. 4 gets up, and when realizing Schmidt trigger as Fig. 1, the rising edge of input signal and trailing edge all can by time delay (320nS+28nS)=348nS.
Seal in ammeter in the supply, the operating current of Fig. 4 circuit is 2.47mA.When realizing Schmidt trigger with Fig. 4 circuit two-stage series connection, operating current is 4.95mA.
The time delay of first embodiment of the present invention Schmidt trigger is 182.7nS, is (182.7 ÷ 348)=52.5% of prior art.The operating current of first embodiment of the present invention Schmidt trigger is (4.06 ÷ 4.95)=82% of prior art.
Triode in discrete component selected by first embodiment of the invention is withstand voltage all at 40V, so even if this circuit is upgraded to 12V operating voltage, such output level is just between 0.3V to 11.7V, peak-to-peak value, up to 11.4V, is enough to the metal-oxide-semiconductor driving cut-in voltage very high.For those skilled in the art, rise to 12V from 5V, operating current can significantly rise, and delay time declines because of the rising of work simultaneously, at this moment can adjust the resistance of the 3rd resistance R103, the 4th resistance R104, the 5th resistance R105, allow the operating current of circuit of the present invention drop to reasonable level.
By above-mentioned Data Comparison, can see, if the present invention is made integrated circuit, so, by the technique of identical at present TTL integrated circuit, the present invention shortens to original about 52.5% delay time equally.
second embodiment
Fig. 8 shows the circuit theory diagrams of second embodiment of the invention; On the basis of the first embodiment, increase by the 6th resistance R106, disconnect the connection between this of the 4th triode T104 and working power end, seal in the 6th resistance R106.Namely the emitter of the 4th triode T104 connects working power end by the 6th resistance R106.
The resistance of the 6th resistance R106 is 43 Ω.
Measured signal is 166.6nS by time delay, in order to save length, no longer provides the sectional drawing of resolution chart here.
Seal in ammeter in the supply, the operating current of the second embodiment is 4.04mA, slightly declines.
The place different from the first embodiment, when the 1st triode T101 saturation conduction, actual measurement saturation voltage drop is 0.15V, so the terminal voltage sum of the 3rd resistance and the 4th resistance is 5V-0.15V=4.85V, so the terminal voltage of the 4th resistance is 1.12V, and so the maximum output current of the 4th triode T104 is limited in
(1.12V-0.7V) ÷ 43 Ω=9.8mA ... formula (6)
Achieve and the maximum output current of circuit is limited, resistance is sealed in emitter due to the 4th triode T104, be equivalent to the input impedance that improve this grade of T104, improve the response speed of this grade, therefore the wastage in bulk or weight electric current of circuit slightly reduces, the time delay of circuit simultaneously is also slightly shortened, and shortening to 166.6nS by the 182.7nS of the first embodiment, is (166.6 ÷ 348)=47.9% of prior art.
Further increasing performance of the present invention.The consistency of discrete component is not very good, conveniently produces, and can increase the 7th resistance, the 8th resistance, the 7th resistance on string in the 1st transistor base, the 8th resistance on string in the 2nd transistor base, and other annexation is constant; Here it is the circuit shown in the 3rd embodiment.
3rd embodiment
Fig. 9 shows the circuit theory diagrams of third embodiment of the invention; On the basis of the first embodiment, increase the 7th resistance R107, the 8th resistance R108, the 7th resistance R107 on string in the 1st triode T101 base stage, the 8th resistance on string in the 2nd triode T102 base stage, other annexation is constant; This just obtains the 3rd embodiment circuit.Other annexation is with the first embodiment.
Wherein design parameter is: the 1st resistance R101 is 2.2K, the 2nd resistance R102 is 10K, the 3rd resistance R103 is 5.6K, the 4th resistance R104 is 2.2K, the 5th resistance R105 is 5.6K, 7th resistance R107 and the 8th resistance R108 is 100 Ω, 1st triode T101, the 2nd triode T102, the 3rd triode T103 are S9018 high-frequency triode, 4th triode T104 is the 2N5401 of low multiplication factor, and its characteristic frequency is f
t=400MHz.Working power end V+ is 12V direct current.
The oscilloscope of the isolating transformer of input, signal source and operating frequency, observation is identical with in embodiment one, and owing to having selected the pipe that characteristic frequency is higher, although each resistance is all increased, measured signal is 116.2nS by time delay.In order to save length, no longer provide the sectional drawing of resolution chart here.
Seal in ammeter in the supply, the operating current of the 3rd embodiment is 3.64mA.
Realize goal of the invention equally.
In fact, increase the 7th resistance R107, the 8th resistance R108 and change a little Europe into by 100 Ω, the emitter of going here and there at the 1st triode T101, the 2nd triode T102, effect is the same.Here no longer analyzing examples.
Equally in the third embodiment, add the 6th resistance R106, disconnect the connection between this of the 4th triode T104 and working power end, seal in the 6th resistance R106 and still can realize goal of the invention, because principle is simple, discussed above, and no longer drew here, illustrate.
Improve further as above-mentioned first embodiment, the second embodiment, present invention provides a kind of method for designing of integrated circuit, 1st triode and the 2nd triode are a two collector electrode triode, namely base stage, emitter are common, and make the triode of two collector electrodes, the 4th embodiment that Here it is.
4th embodiment
Figure 10 shows the circuit theory diagrams of fourth embodiment of the invention; Comprise the 1st resistance R101, the 2nd resistance R102, the 3rd resistance R103, the 4th resistance R104, the 5th resistance R105,1st triode T101, the 3rd triode T103, the 4th triode T104, wherein, 1st triode T101 is the triode of two collector electrodes, two collector electrodes are respectively the 1st collector electrode C1 and the 2nd collector electrode C2,2nd triode T102, the 3rd triode T103 are NPN type triode, 4th triode T104 is PNP type triode, comprise 4 terminals, signal input part Vin, signal output part Vout, working power end V+, earth terminal simultaneously; Its annexation is: one end of the 1st resistance R101 is signal input part Vin, and the other end of the 1st resistance R101 connects the base stage of the 1st triode T101, connects one end of the 2nd resistance R102 simultaneously; The other end of the 2nd resistance R102 is the signal output part Vout of Schmitt trigger circuit, connects the collector electrode of the 3rd triode T103 and the collector electrode of the 4th triode T104 simultaneously; The emitter of the 1st triode T101 and the emitter of the 3rd triode T103 are all connected to earth terminal, the 1st collector electrode C1 of the 1st triode T101 connects the 4th resistance R104 by the 3rd resistance R103, the other end of the 4th resistance R104 connects working power end V+, 3rd resistance R103 is also connected the base stage of the 4th triode T104 with the tie point of the 4th resistance R104 simultaneously, and the emitter of the 4th triode T104 connects working power end V+; The 2nd collector electrode C2 of the 1st triode T101 connects working power end V+ by the 5th resistance R105, and the 2nd collector electrode C2 is connected the base stage of the 3rd triode T103 with the 5th resistance R105 tie point simultaneously;
Existing integrated circuit technology realizes this common base, common emitter, and " triode " of multicollector is very a piece of cake, the triode of this structure is very common in various integrated circuit, and according to the operation principle in technical scheme, the 4th embodiment realizes the object of the invention equally.
5th embodiment
Figure 11 shows the circuit theory diagrams of fifth embodiment of the invention; On the basis of the first embodiment, substitute the 5th above-mentioned resistance R105 with constant-current source I101.Other annexation is constant.
The output current of constant-current source I101 is 2mA, and model is E-202.Other parameter is identical with the first embodiment, and same realization of actual test finds object.
When supply voltage raises, the electric current due to this road of I101 no longer becomes large, so the total operating current of the circuit of the 5th embodiment rises comparatively slow, further increases power adaptation.
For the embodiment of four above, this method can be used, 5th resistance R105 is replaced to constant-current source, constant-current source technology is ripe known technology, Figure 12 is the constant-current source schematic diagram of the first low cost, Figure 13 is the constant-current source schematic diagram of another kind of low cost, wherein triode T201 is constant current output pipe, resistance R202 is biasing resistor, regulating resistance R201 just can change the size of continuous current, in fig. 12, realize constant current with the amplification of triode T202, when certain reason makes output current become large, so the side pressure of resistance R201 is fallen and can be become large, at this moment the base current of triode T202 becomes large, its collector current increases, cause pressure drop on resistance R202 large, the base voltage equaling triode T201 raises, thus cause the collector current of triode T201 to decline.And in Figure 13, when certain reason makes output current become large, so the side pressure of resistance R201 is fallen and can be become large, because diode D201 and D202 connects, be equivalent to the voltage-stabiliser tube of a 1.2V to 1.4V, at this moment, the side pressure of resistance R201 is fallen and can be become large, the emitter of triode T201 can be caused to reduce to the voltage of base stage, and so therefore the collector current of triode T201 declines, and gets back on constant current point.Wherein 301 ports connect in working power, on the collector electrode that 302 ports meet the 2nd triode T102 or in Figure 10 the 1st triode T101 the 2nd collector electrode C2 on.
Above lifted embodiment, after powering on, when not having triggering signal, its output is all low level, and power on if expect the circuit exported as high level, adds conventional electrify restoration circuit at input to working power end.
Below be only the preferred embodiment of the present invention; it should be noted that; above-mentioned preferred implementation should not be considered as limitation of the present invention; for those skilled in the art; without departing from the spirit and scope of the present invention; some improvements and modifications can also be made; as on resistance R102, R103 and on speed-up capacitor; these improvements and modifications also should be considered as protection scope of the present invention; here no longer repeat by embodiment, protection scope of the present invention should be as the criterion with claim limited range.
Claims (9)
1. a Schmitt trigger circuit, comprise: the 1st resistance, the 2nd resistance, the 3rd resistance, the 4th resistance, the 5th resistance, 1st triode, the 2nd triode, the 3rd triode, the 4th triode, the 1st described triode, the 2nd described triode, the 3rd described triode are NPN type triode, the 4th described triode is PNP type triode, also comprise 4 terminals, signal input part, signal output part, working power end and earth terminal simultaneously; Its annexation is: one end of the 1st described resistance is signal input part, one end of the 2nd resistance described in other end connection of the 1st described resistance, the other end and the tie point of one end of the 2nd described resistance of the 1st described resistance are also connected the base stage of the 1st described triode and the base stage of the 2nd described triode simultaneously; The other end of the 2nd described resistance is described signal output part, the collector electrode of the 3rd triode described in described signal output part connects and the collector electrode of the 4th described triode; The emitter of the emitter of the 1st described triode, the emitter of the 2nd described triode and the 3rd described triode is all connected to described earth terminal, the collector electrode of the 1st described triode is by the 4th resistance described in the 3rd described resistance connection, the working power end described in other end connection of the 4th described resistance, the 3rd described resistance is also connected the base stage of the 4th described triode with the tie point of the 4th described resistance simultaneously, the working power end described in emitter connection of the 4th described triode; The collector electrode of the 2nd described triode is by the working power end described in the 5th described resistance connection, and collector electrode and the tie point of the 5th described resistance of the 2nd described triode are connected the base stage of the 3rd described triode simultaneously; The 1st described triode and the 2nd described triode are the triode of same model.
2. Schmitt trigger circuit according to claim 1, is characterized in that: also comprise the 7th resistance, the 8th resistance; The other end and the tie point of one end of the 2nd described resistance of the 1st described resistance are connected the 7th described resistance one end, the 8th described resistance one end simultaneously, the base stage of the 1st triode described in other end connection of the 7th described resistance, the base stage of the 2nd triode described in other end connection of the 8th described resistance, other annexation is constant; Or the other end of the 1st described resistance is connected the base stage of the 1st described triode, the base stage of the 2nd described triode with the tie point of one end of the 2nd described resistance simultaneously, the emitter of the 1st described triode is connected to described earth terminal after the 7th described resistance, the emitter of the 2nd described triode is connected to described earth terminal after the 8th described resistance, and other annexation is constant.
3. Schmitt trigger circuit according to claim 1 and 2, is characterized in that: the 1st described triode and the 2nd triode are that a base stage, emitter are common, have two collector electrode triodes of two collector electrodes.
4. Schmitt trigger circuit according to claim 1 and 2, is characterized in that: the 5th described resistance replaces with 1 constant-current source.
5. Schmitt trigger circuit according to claim 3, is characterized in that: the 5th described resistance replaces with 1 constant-current source.
6. Schmitt trigger circuit according to claim 1 and 2, is characterized in that: also comprise the 6th resistance, between the emitter that the 6th described resistance is connected to the 4th described triode and described working power end.
7. Schmitt trigger circuit according to claim 3, is characterized in that: also comprise the 6th resistance, between the emitter that the 6th described resistance is connected to the 4th described triode and described working power end.
8. Schmitt trigger circuit according to claim 4, is characterized in that: also comprise the 6th resistance, between the emitter that the 6th described resistance is connected to the 4th described triode and described working power end.
9. Schmitt trigger circuit according to claim 5, is characterized in that: also comprise the 6th resistance, between the emitter that the 6th described resistance is connected to the 4th described triode and described working power end.
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| CN201210334692.4A CN102904549B (en) | 2012-09-11 | 2012-09-11 | Schmitt trigger circuit |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN105471421B (en) * | 2014-09-10 | 2019-11-08 | 南车株洲电力机车研究所有限公司 | A kind of level shifting circuit |
| CN107017864B (en) * | 2016-01-28 | 2019-11-05 | 深圳市汇顶科技股份有限公司 | Trigger and oscillatory system |
| CN108306641B (en) * | 2018-03-29 | 2023-08-01 | 广东电网有限责任公司 | Phase frequency tracking device for partial discharge test |
| CN109560084A (en) * | 2018-10-16 | 2019-04-02 | 天津大学 | Flexible Schmidt circuit based on flexible substrate |
| CN111504168B (en) * | 2020-04-28 | 2022-02-01 | 上海深拓液压技术有限公司 | Solenoid valve fault detection circuit capable of deducing displacement change through inductance change |
| CN115085673B (en) * | 2022-07-22 | 2023-05-19 | 成都信息工程大学 | Triode oscillator with deep negative feedback structure |
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