CN1022279C - Ultra high gain direct coupling amplifying circuit - Google Patents

Abstract

The present invention relates to an interstage directly-coupled multi-stage signal amplifying circuit which is mainly used for amplifying an AC signal. With the adoption of the present invention, directly-coupled amplifying circuits with any output form, different power, different gains and different impedance can be designed. The present invention has the advantages of simple circuit structure, convenient adjustment, stable working point, and difficult occurrence of self-excitation; in addition, the circuit has good resistance to overload and the short circuit of a load, and high ratio of the gain to quiescent current.

Description

Ultra high gain direct coupling amplifying circuit

The present invention is an electronic circuit, is the direct-coupled multistage amplifier circuit of inter-stage.Be used for amplifying the AC signal of tool certain frequency scope.

As everyone knows, in the multistage amplifier circuit design, for satisfying circuit the frequency response of broad is arranged, particularly the lower signal of frequency there is good amplification effect, interstage coupling often adopts direct-connected mode, and seldom adopts capacitor or inductance device to realize coupling.But so, just bring the quiescent point instability of circuit to wait other disadvantage.For overcoming these shortcomings, and design numerous multistage amplifier circuits, although the biasing circuit of these circuit, input stage, intergrade and output stage all have their own characteristics each, but present most of multistage amplifier circuit, comprise that inter-stage adopts direct-coupled circuit, still have some not satisfied places, as be easy to generate self-oscillation, anti-overload ability is poor, load can not short circuit shortcoming, it is low to gain, and influences its result of use, therefore, a kind of multistage straight coupling amplifying circuit that can overcome above-mentioned shortcoming is actual needs.

The application object of introduction of the present invention is a kind of high a kind of direct coupling multistage amplifying circuit of above-mentioned shortcoming gain that overcome.

Casacade multi-amplifier of the present invention amplifies high frequency, intermediate frequency and low frequency signal, has the Hz-KHz of broad.Amplifying circuit is by input stage, and preamplifier state and promotion level are made interstage amplifier section, and power-amplifier stage is formed.

Preamplifier state is done preliminary the amplification to signal.For improving the quality of preamplifier state, be provided with a dynamic constant pressure source, this power supply can guarantee that the preamplifier state interstage voltage is stable.Amplifying signal is sent into the promotion level and is done the electric current amplification, the power output circuit of this promotion level adopts the purce complerentary circuit form of a kind of " BTL " type, known purce complerentary circuit has one group of opposite polarity triode, one is the positive-negative-positive pipe, and one is NPN type pipe, and the collection utmost point of said NPN type pipe connects positive supply, the collection utmost point of positive-negative-positive pipe connects negative supply, the level of penetrating of two pipes links to each other, and joins with load, does emitter-base bandgap grading output.The base stage of two triodes links to each other with the prime input signal, and is connected to a circuit that the ground level quiescent voltage is provided simultaneously.Said circuit is made up of one group of crystal diode, for back one-level transistor base stage provides fixed-bias transistor circuit.

The promotion level of this programme has bigger improvement to known circuit, be provided with two opposite polarity triodes equally, but in order to reduce the base stage quiescent current of flow path two pipes, the base stage of two transistors all adjunction current-limiting resistance, said current-limiting resistance one end links to each other with base stage, and an end links to each other with the fixed-bias transistor circuit point that base voltage is provided, the positive and negative point of its emitter-base bandgap grading and power supply, or mid-point voltage is continuous, and collector electrode links to each other with the base stage of subsequent conditioning circuit by a resistance.

It is relevant to add definite collector current and the circuit voltage with the corresponding levels that is connected on the resistance of resistance on the two pipe base stages, and relevant with prime input impedance, the dynamic current size that is input to base stage at the corresponding levels with prime is relevant.

For the dynamic current that prestage is outputed to promote the level base stage be not subjected to add the influence of resistance, adopted the preposition utmost point of dynamic constant current output, can reduce to promote level base stage quiescent current to reach, again can minimal losses dynamic current be presented to the base stage that promotes level, it is fixed that the input impedance of prestage is put arbitrarily.

Said dynamic constant-current source is made up of a transistor at least, and its emitter-base bandgap grading and power supply join, and the collection utmost point connects load, and base stage is joined by resistance and power supply.

The electric current that dynamic constant-current source is exported to form the fixed bias point, provides bias voltage, quiescent current and dynamic current so that collect a utmost point to the promotion level in last generation pressure drop by at least one group of crystal diode.

The collector electrode that this programme promotes two transistors of level has the connection different with known technology.The collector electrode of known technology generally directly joins with power supply by resistance, and when back level load short circuits or overload, the promotion pipe will bear very big power, easily it be burnt.Two collector electrodes of this programme and the base stage of subsequent conditioning circuit are directly joined by a resistance, thereby have overcome the defect of burning pipe, and said subsequent conditioning circuit comprises a phase inverter at the same level, a power amplifier.

Said homopolarity inverting amplifier circuit is made up of one group of resistance and the inverter transistor triode that can adjust resistance at least, and an end of resistance extremely links to each other with a promotion level transistor collection, and the other end links to each other with the base stage of inverter transistor triode.

This programme is with above-mentioned preposition amplification and promote level as intermediate circuit, carries out power amplification at last, and power amplifier is output as a kind of improved " BTL " pattern, and its advantage is power utilization rate height, and anti-overloading performance is good.Its structure has mainly adopted the purce complerentary coupled modes.The power amplifier system that this programme links to each other with the promotion circuit amplifies with two groups of transistors are complementary, in on the same group, two complementary amplifications of power amplifier transistor, the collection utmost point of two power amplifier transistors links to each other with load, emitter-base bandgap grading links to each other with power supply, the base stage of one pipe extremely links to each other with the collection that promotes pipe by a resistance, and the base stage of another pipe extremely links to each other with the collection of phase-reversing tube by a resistance.

For stablizing the quiescent point of whole system, this programme has designed a direct current degeneration factor, and native system is different with known technology.The loop negative feedback of known technology plays negative feedback too to current intelligence, this programme has overcome the shortcoming of known technology, designed dc loop circuit negative feedback makes and exchanges negative feedback is zero substantially, its structure has the one group of adjustment link that can adjust feedback quantity at least, one end links to each other between load and the electric capacity, and an end links to each other with the base stage of the transistor of preposition amplification.

The direct current degeneration factor of this programme changes the negative feedback that has very greatly to direct current, and AC signal is not just played negative feedback substantially, thereby gain is high especially.

For making subsequent conditioning circuit in when work, the big caused power source change of electric current does not influence prestage work, ad hoc dynamic stabilized voltage power supply, improves the quality of voltage of prestage, reaches and stablizes prestage working point purpose.

The interstage coupling of the amplifier of this programme adopts directly coupling, do not use electric capacity and inductance to carry out the interpolar coupling, but because above-mentioned measure can not produce the quiescent point instability and circuit produces disadvantages such as vibration, thereby the suitable especially circuit of making this programme of the mode of integrated circuit.

Can recognize by above-mentioned narration and the objective of the invention is to: an improved purce complerentary output circuit is provided, improve the quality that base stage provides quiescent current; When not having AC signal, base stage only allows to flow through quiescent current seldom, when AC signal, has enough dynamic currents to be sent to subordinate again and amplifies.

Another object of the present invention is: the promotion level transistor in the improvement known technology bears the shortcoming of load short circuits ability.

Further object of the present invention is, makes the interstage voltage of the prestage in the amplifier stable, can stand the fluctuation of subsequent conditioning circuit voltage.

Purpose of the present invention also has: circuit can be set up the quiescent point of stablizing its each link automatically.

Purpose of the present invention also has: the power that improves the output of output stage " BTL " circuit.

Purpose of the present invention also has: newly-designed multistage amplifier circuit is easy to use integrated circuit, or discrete component is realized.

Through the narration of such scheme, can recognize that purpose of the present invention can reach.

Be further described below by embodiment.

Fig. 1, be the design frame chart of this programme:

Fig. 2, be the circuit theory diagrams of this programme embodiment.

Now concrete scheme of the present invention is described as follows: the block diagram that Figure 1 shows that this programme in conjunction with diagram.

The signal source of this programme (31) converts physical message to the signal of telecommunication by various transducers and obtains, and this signal of telecommunication has various frequencies.By the design of the frequency of signal decision subsequent conditioning circuit, the selecting for use etc. of element.The frequency range of present embodiment is intermediate frequency and low frequency signal.Signal is sent into preamplifier state (32) and is carried out voltage amplification, and this level is provided with dynamic constant-current source (34) and dynamic stable-pressure device (33) simultaneously, and the gained signal is sent into promotion level (35) and carried out the electric current amplification.The signal part via line (39) that certain current strength is arranged that is produced is sent into paraphase amplifying device at the same level, and the signal warp (41) after the paraphase is sent into power amplifier device (36).Another part signal warp (40) that promotes level is directly sent into power amplification device (36).Signal through power amplification finally promotes load (37), and said load comprises electric horn or other transducing head.For stablizing the static working current of whole circuit, from load (37) warp (42), draw a direct current electric current warp (43) to preamplifier state (32), the size of feedback quantity is adjusted by loop negative feedback arrangement (38), but this reponse system is not fed back AC signal, thereby has improved the gain of the AC signal of entire circuit greatly.

Fig. 2 is for realizing this programme physical circuit figure.Signal source (31) is held input from a, b.Present embodiment is made signal source is sent into preamplifier state through signal coupling capacitance (27) input stage with the crystal pick-up of phonograph.The preamplifier state of present embodiment is made of triode transistor (1), and its base stage and signal source are formed the loop, and the collection utmost point has a current source loads (2) the collection utmost point and links to each other with the input circuit that promotes level simultaneously.

Said promotion level is made up of two different transistor (3) and (4), two diodes (11), (12) and resistance (15), (16) of model.Transistor (3) is a positive-negative-positive, and transistor (4) is the NPN type, and the emitter-base bandgap grading of two pipes links to each other, and ground connection, and the collection utmost point of two pipes directly is connected with the input circuit of subsequent conditioning circuit by a resistance.The base stage of triode transistor (3) links to each other with the negative pole of diode transistor (12) with the other end of resistance (16), and the collection utmost point mat of its tie point and its preamplifier state (1) closes; The base stage of triode transistor (4) links to each other with resistance (15) one ends, and the other end of resistance (15) links to each other with the positive pole of diode transistor (11), the collection utmost point coupling of its point of contact and triode transistor (2).

In above-mentioned promotion level, triode transistor (2) is similar to dynamic constant-current source, diode transistor (11), (12) supply with complementary work bias current of managing (3) and (4) as an approximate fixed-bias transistor circuit, the resistance that is connected in series on the base stage of two pipes (15), (16) value is by this circuit voltage, (3), (4) collected current of pipe and input resistance decision, this resistance decrement the base current of two transistors (3) and (4), so also make in the subsequent conditioning circuit and reduce about transistorized collected current, the quiescent current of entire circuit is little like this, comparatively speaking, the shared ratio of quiescent current and power output is just little; The dynamic constant-current source effect that other aspect forms owing to transistor (2), though base resistance (15), (16) are arranged, but still can guarantee that AC signal has enough dynamic currents, unlikely generation amplifying signal unnecessary loss when entering the promotion level.

Dynamically constant-current source is made up of transistor (2), pipe (2) is that a positive-negative-positive pipe, its emitter-base bandgap grading connect positive supply, its utmost point connects negative supply by a resistance (13), and the collection utmost point connects load, and the dynamic constant-current source of being made up of transistor (2) of present embodiment also is the load of prestage (1) simultaneously.

Promote the level amplifying signal and carry out power amplification at last.The output stage of forming " BTL " power amplifier in the present embodiment by triode transistor (5), (6), (7), (8), resistance (17), (18), power amplifier also comprises one group of paraphase amplifying device at the same level of being made up of transistor (9) and (10), resistance (19), (20) and variable resistor (21) and (23), said elements and circuit, has just formed new " BTL " circuit.

In " BTL " circuit of existing design, power amplifier transistor (5) and (8) are one group, and (6) and (7) are another group, and in same group, the collection utmost point of two power amplifier transistors all joins with load (22), and emitter-base bandgap grading and power supply join.

Two groups of paraphase amplifying devices at the same level are arranged in " BTL " circuit of the design.One group that couples with triode transistor (3) is resistance (19), and adjustable resistance (23) and triode (9) constitute; And a group of coupling of triode transistor (4) is resistance (20), and adjustable resistance (21) and triode transistor (10) constitute.Its paraphase amplification principle illustrates with one group.For example said series resistance (20) and (21), one end and the collection utmost point coupling that promotes level triode transistor (4), the base stage of one end and inverted triode (10) links, to send into the base stage of paraphase triode transistor (10) from the shunting signal that the collection utmost point that promotes level triode transistor (4) is obtained, the shunting signal size obtains by adjusting resistance (21), but does not influence the signal of sending into power amplifier triode transistor (5).Shunting signal is sent into the base stage of power tube (8) after inverter transistor triode (10) paraphase is amplified, like this, be added in the load (22) that the lotus root of connecting with the two pipe collection utmost points closes through power amplifier transistor (5) and (8) amplifying signal voltage, equally, the paraphase amplifying device at the same level that another group is made up of resistance (19), (22) and transistor (9) is also finished same function with power tube (6) and (7).

In order to stablize the quiescent point of entire circuit, the embodiment of this programme is provided with a loop direct current negative feedback.One end of feedback is taken out by the intersection point place of load and capacitance (29), through feedback adjusting link (26), the other end links to each other with the base stage of preposition amplifying stage transistor (1) by resistance (14), when the quiescent point in whole loop changes, the base stage that quiescent current is delivered to preamplifier state through feedback element (26) is adjusted, but seldom pass through feedback loop from the AC signal that load (22) is passed through, directly from enter the path that (7) pipe or (8) pipe form every electric capacity (29).So owing to exchange the very little gain that improves entire circuit widely of negative feedback.Said capacitance (29) one ends are connected with load (22) and feedback end, and the collection of other end power tube (7) and (8) extremely links to each other.

For improving the quality of preamplifier state, the embodiment of this programme is provided with a dynamic stabilized voltage power supply in prestage, is made up of diode transistor (45) and electric capacity (28).Said diode transistor (45) one termination powers, an end links to each other with electric capacity (28).Electric capacity (28) is connected across on the emitter-base bandgap grading of the collection utmost point of constant-current source triode transistor (2) and preamplifier state transistor, when the subsequent conditioning circuit load that links to each other with preamplifier state has fluctuation, when causing whole voltage to change, because electric capacity (28) has the trend of opposing change in voltage, thereby the change in voltage at two ends is less, has guaranteed that the terminal voltage of preamplifier state and constant-current source is basicly stable.

Present embodiment is as follows for the amplification principle of signal: when the signal of telecommunication (31) enters the base loop of prestage (1) from a, b end, enter from the collection utmost point through the signal of voltage amplification and to promote level.When signal during at positive half cycle, signal enters the base loop that promotes pipe (4), amplifying signal is through the collection utmost point output of triode (4), signal is divided into two-way, one the tunnel is amplified into the base stage of power tube (8) mutually through example at the same level, signal is added in the load (22) from the output of (8) pipe collection utmost point, and another road directly is added in the load (22) by power tube (5) amplification.

In like manner, when signal is in negative half period, be added in the load (22) through another circuit component amplification, principle is to last similar.

The power supply of present embodiment is ± 3V, and this circuit Maximum Power Output is 3W, and electric capacity (27) is 0.1Uf, and (28) are 1000uf, and (30) are 50uf.Resistance (13) is 3 megaohms, (14) be 1 megaohm, (15), (16) are 30 kilo-ohms, (17), (18) are 0.1 kilo-ohm, the impedance of load (22) is 8 Europe, adjustable resistance (21), (23) are 680 kilo-ohms, and (25), (24) are 0.1 kilo-ohm, and adjustable resistance (26) is 5 megaohms.

Used electric crystal triode (2), (3), (10) are positive-negative-positive small-power silicone tube, (1), (4), (9) are NPN small-power silicone tube, (5), (7) be the PNP high power valve, (6), (8) are NPN type power tube, its value of magnification is all about 100.And has a little electric current amplification characteristic.

Claims (7)

1, a kind of ultra high gain direct coupling amplifying circuit, comprise prestage, promote level and power-amplifier stage, described promotion level has a pair of polarity opposite, is connected into the transistor of complementary type, its emitter-base bandgap grading links to each other with the positive and negative point or the mid-point voltage of power supply, it is characterized in that:

Respectively be connected to the current-limiting resistance of a suitable resistance between the base stage of a pair of transistor and the fixed-bias transistor circuit point, the collection utmost point links to each other with the base stage of subsequent conditioning circuit by resistance.

2, a kind of ultra high gain direct coupling amplifying circuit according to claim 1 is characterized in that: the prestage load is a dynamic constant-current source.

3, a kind of ultra high gain direct coupling amplifying circuit according to claim 1 and 2, it is characterized in that: said dynamic constant-current source provides fixed-bias transistor circuit and dynamic current by one group of crystal diode for the base stage that promotes the level transistor, and each extremely links to each other the head end of diode and tail end with the collection utmost point of dynamic constant-current source and the collection of preamplifier state.

4, a kind of ultra high gain direct coupling amplifying circuit according to claim 1, it is characterized in that: paraphase amplifying device at the same level, the output signal paraphase of level will be promoted, input to power amplifier device, at least form by one group of adjustable resistance and an inverter transistor triode, one end of resistance couples with promoting the level transistor collection utmost point, and the other end links to each other with the inverter transistor transistor base.

5, according to claim 1 or 4 described a kind of ultra high gain direct coupling amplifying circuits, it is characterized in that: the input signal of efficient amplifying device comprises in-phase signal and the reversed phase signal that promotes level output.

6, a kind of ultra high gain direct coupling amplifying circuit according to claim 1, it is characterized in that: power amplifier system amplifies with two group transistors are complementary, in on the same group, two power tube collection utmost points link to each other with load, emitting stage links to each other with power supply, wherein one group of ground level links to each other with the collector electrode that promotes level, and another group ground level links to each other with the output of the routine amplifying device mutually of peer.

7, ultra high gain direct coupling amplifying circuit according to claim 1, it is characterized in that: be provided with a direct current negative feedback, has the one group of adjustment link that can adjust feedback quantity at least, the direct current negative-feedback signal takes out an end and load one end and capacitance and connects, and the other end links to each other with the input of preamplifier state.

Images