JPS5945255B2 - Output pulse time width control circuit that takes monotonically increasing waveform pulses as input - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a time width control circuit for monotonically increasing waveform pulses, such as triangular waves or similar waveform pulses.

The input/output characteristics of a transistor differential amplifier is used for the pulse time width control circuit that extracts input waveform pulses that monotonically increase over time, such as triangular waves or similar waveform pulses, as output waveform pulses of arbitrary time width. something is well known.

FIG. 1 is a main part configuration diagram showing -flI of the above-mentioned known pulse duration control circuit using a transistor differential amplifier, in which the transistors Q1, Q2, . A triangular wave or a similar waveform pulse v1 is applied to one input terminal 1 of the , and an arbitrary steady voltage v2 is applied to the other input terminal 2.
, an output pulse whose pulse duration is arbitrarily controlled depending on the magnitude of the steady voltage V2 can be extracted from the output terminal of the level shift drive circuit B.

In other words, when an input shaping pulse that monotonically increases with time t as shown in input terminal 1 is applied, and a steady voltage v2 is applied to the other input terminal 2, the collector current Ic of transistor Q1 increases from zero to ■. Input voltage V1 at time Ta (
Ta) is approximately 26 m at room temperature where h is kT/q (k: Boltzmann's constant, q: electron charge amount, T: absolute temperature).
Assuming that V is a well-known physical quantity, Vl(Ta)-=V2-M? n(Ic3/l-1)
(2), which can be obtained by inversely transforming Ta
From the following equation (3), the time width Ta from when the collector current Ic1 of the transistor Q1 of the differential amplifier A reaches I from zero to activate the level shift drive circuit B in the subsequent stage, that is, the output pulse. It will be explained that the time width can be arbitrarily controlled by the level value of the steady voltage v2.

However, as can be seen from equation (3), the time width Ta of the output pulse is determined by the offset voltage h in addition to the value of the steady voltage v2.
It is also influenced by en (I c 3/I −1).

Since the value of the offset voltage usually differs depending on the individual circuit, that is, for each product, the value of the offset voltage is
In order to obtain a, the steady voltage V2 is different for each product.
It is technically extremely difficult to uniquely define all voltages at the same level.

In particular, in a circuit that supplies this steady voltage v2 by resistance division from a common DC power supply Vcc, it is impossible to make the time width of the output pulse equal unless a different division resistance ratio is provided for each product, and this is not done. Even if a change occurs in the voltage value of the DC power supply Vcc, it becomes technically meaningless.

In this way, the existence of an offset voltage in a pulse width control circuit using a transistor differential amplifier makes circuit design extremely difficult, makes mass production difficult through integrated circuits, and makes it dependent on the DC power supply voltage. This brings about various inconveniences, such as having

One way to avoid the effects of offset voltage is to
The setting area of the steady voltage v2 is v2>hln(Ic3/l-
It is conceivable to limit it to 1) and use it in a state where the offset voltage component can be ignored, but such a mode of use naturally limits the level variable range of the steady voltage V2 to a narrow range, and the control range of the output pulse time width. cannot be spread over a wide area.

In this case, there may be a remedy to raise the maximum level of the steady voltage V2 by increasing the voltage of the DC power supply Vcc sufficiently, but this is not preferable from the viewpoint of circuit technology.

Another method for avoiding this is to bring the value of the collector current (2) of the transistor Q1 close to the value (A) of the collector current Ic3 of the transistor Q3 of the constant current circuit, and set the operating conditions such that the offset voltage can be considered to be almost zero. There is.

However, under this operating condition, the input current value of transistor Q1 has a current amplification rate of β.

Since I/791 must be given as a signal, the input impedance naturally decreases.

Therefore, the circuit will not operate unless the input waveform pulse V1 is sufficiently large, making it completely unsuitable when a relatively small waveform pulse is desired to be input.

In addition, when a waveform pulse with aV/at close to zero is input, a waveform output that always maintains a constant value is obtained,
The function as a pulse duration control circuit is completely lost.

Simply trying to avoid the effects of offset voltage in this way introduces new undesirable phenomena such as limiting the control range of the output pulse time width or lowering the input impedance. It's just that.

An attempt to compensate for offset voltage using a circuit was published in Japanese Patent Publication No. 45-29846 ``Transistor Type Differential Amplifier''.
proposed in the specification.

According to this proposal, a series circuit of a diode and a resistor is inserted between the common emitter of the pair of transistors of the differential amplifier and the base of each, and the current is supplied from a new constant current circuit. The constant current is appropriately shunted to each base side in a direction to compensate for the offset current through adjustment of the resistor.

This proposed circuit is an effective means of solving the problem, unlike simply trying to avoid the effects of offset voltage.

In particular, temperature compensation characteristics can be improved by inserting resistors into the base of each transistor by selecting resistance values determined by the temperature coefficients of the circuit elements.

However, selecting a resistance value based on the temperature coefficient of each circuit element is theoretically impossible, but determining a specific value is not easy.
In addition, in order to integrate the selected resistance value into an integrated circuit with high precision, there are considerable restrictions from the viewpoint of production technology, so improvement in temperature compensation characteristics cannot be said to be very promising and is not a realistically effective means.

As described above, the proposed circuit has difficulty in achieving a sufficient temperature compensation circuit configuration, and still includes deficiencies in circuit design technology.

In view of the above circumstances, the present invention seeks to provide an output pulse duration control circuit which takes monotonically increasing waveform pulses as input and is provided with circuit means for offset voltage compensation that can be sufficiently electrically compensated. The purpose is to increase the degree of freedom in circuit design technology, such as lowering voltage, increasing input impedance, and stabilizing temperature characteristics, and to facilitate the fabrication of integrated circuits.

This will be explained in detail below using the drawings.

FIG. 2 is a connection circuit diagram of an embodiment of the present invention, in which Ql and Q2 are a pair of transistors each having an input terminal 1 or a control terminal 2 and constituting a known differential amplifier, Q3 . R3,
R1 and Dl are transistors, resistors, and diodes that constitute the constant current power supply circuit of the differential amplifier, and vBEl
, vBE2. and VBE3 are the transistors Q1. The base-emitter junction voltages of Q2 and Q3 are shown.

A resistor R is connected between the base and control terminal of the transistor Q2.
A constant current circuit consisting of a transistor Q, an emitter resistor R4, and a diode D2 is inserted between the base and collector of the transistor Q4, and the collector of the transistor Q4 is connected to the base terminal of the resistor Ros. A transistor Q5, which is set to a common base potential with the transistor Q3 of the constant current power supply circuit, is connected between the base and the constant current power supply circuit through an emitter resistor R5 so that a constant current is always supplied to the base.

Now transistor Q1. Constant current Ic3 is supplied to Q2 from the constant current power supply circuit, and Ic3. As is well known, the offset voltage VosO value generated between the two bases when the collector current of Ic2 is flowing is Vo S = VBE2 - vBE1 = M if the saturation currents Is are equal.
'nI c 2/I s-M? n I c /I 5=
hAnIc2/Ic1-hAn(Ic3/Ic
1-1)
(4) becomes.

However, h is a physical quantity representing kT/q, which has already been explained.

Transistor Q3. If the characteristics of Q5 are aligned, the base-emitter junction voltage is set equal to VBE3="BF2", and the emitter resistances R3 and R5 are set equally, the base potential v
From the following formula % formula % (5), the transistor Q3. The collector currents Ic3°Ic of Q5 take equal values.

That is, the collector current Ic5 of the transistor Q5 is made into a constant current equal to the current c3 of the constant current power supply circuit.

Here, a constant current Ic4 is transmitted from the constant current circuit inserted between the base and collector of the transistor Q2.
4 flows toward the control terminal 2 side of the insertion resistor Ros.

This constant current Ic4 has a common base with the diode D2 and the transistor Q4.
hAnIc5/l5=R4Ic4+M? nIc
4/Is (6), transistor Q3
．． Similar to the relationship with Q5, transistor Q4. If the characteristics of
)'1yR4・AnIc, /Ic 4=h/R4
H11n Ic 3Ac 4 (
7) is related to the constant current Ic3 of the constant current power supply circuit.

In other words, the voltage V'os across the insertion resistor Ros is V'os
=Ros 4c4Ros/R4(h・AnIc 3/I
c4)...(8) If the insertion resistance Ros and constant current c4 are adjusted and selected to be equal to the offset voltage Vos in equation (4), the offset voltage of the differential amplifier can be completely can be compensated for.

At this time, the base voltage of the transistor Q2 is the sum of the steady voltage v2 applied to the control terminal 2 and this voltage V'os, so the monotonically increasing waveform human power pulse v0 shown in equation (1) is applied to the input terminal 1 of the transistor Q1. , collector current ■c
If the level shift drive circuit B at the subsequent stage is set to invert when the voltage 1 reaches Ω, the time width Ta of the output pulse at this time can be calculated using the base voltage of the transistor Q2 and the inserted resistance Ros as shown in equation (3). Ta=V-1(V2) (9
), and after all, it can be uniquely determined only by the magnitude of the steady voltage v2 applied to the control terminal 2.

In the case of a circuit configuration in which the steady voltage V2 is provided by resistance division from the DC power supply Vcc, this magnitude is determined only by the division resistance ratio and there is nothing else involved, so the output pulse width can be determined using this resistance ratio. It is possible to specify it uniquely.

In general, it is very easy to match the transistor characteristics in a monolithic integrated circuit, and it is still preferable to form a resistor using a resistance ratio. Therefore, if the steady voltage V2 is provided by resistance division from the DC power supply Vcc, the present invention can be applied to a monolithic integrated circuit. It can be very easily implemented in circuits and can be mass-produced.

Further, the base of the transistor Q4 is always supplied with a constant current ■c5 that is equal to the current ■c3 of the constant current power supply circuit, and the transistors Q3 and Q5 are set to have the same characteristics, so that the base current of the transistor Q4 ■c5 is a constant current. Since the output current c3 of the power supply circuit is made constant in response to temperature changes, improvement of the temperature compensation characteristics of the circuit can be achieved with an extremely simple circuit configuration and is easy to realize.

Furthermore, from equations (7) and H8), the voltage V across the resistor Ros
'os is V'os=h −Ros/R[nIc5/Ic4=h−
Ros/R4・1n(Ic5/Ic3 ・Ic3/Ic
t4c1/Ic4)=h-Ros/R4(7nIc
3/I c 1+An(I c5/I c3)/(I
c, /I cl) ) ... (1
0), so the current ratio ■c5/■c3 and Ic
It is also possible to design the circuit to such an extent that the second term of the logarithmic ring can be ignored by appropriately selecting 4/■c1.

In this case, the output current c4 of the constant current circuit can be set relatively large, so the insertion resistor RosO value can be set relatively small, and the influence on the base resistance value of transistor Q2 can be avoided to a certain extent, and the low level input It will be suitable for

That is, according to the present invention, the offset voltage of the transistor differential amplifier can be completely compensated for in a circuit with a configuration that is easy to integrate, and the output pulse duration can be uniquely controlled only by the resistance division ratio from the DC power supply Vcc. It is possible to easily realize an output pulse duration control circuit with a relatively free circuit design and effective temperature compensation improvement.

Next, the current amplification rate β of transistor Q6 in circuit B
6) is selected as 1, and a resistor R is connected to its collector terminal.
3.3.R5 with an emitter resistor R7 equal to the base potential of the transistor Q3.3. By inserting a transistor Q7 set to a common potential with Q5, the collector current β6c1 of the transistor Q6 can be made constant to be equal to the collector currents Ics and Ic5 of the transistors Q3 and Q5, respectively.

Therefore, the offset voltage Vos at this time is expressed by formula (4)
By inserting the above relationship into , it can be expressed as Vos=hln(β6-1)Thh#nβ6(lυ).

In addition, the voltage V'os across the insertion resistor Ros that compensates for the offset voltage can be calculated by modifying equation (8): V'os=h-Ros/R4#n(Ic3/Ic1・I
c1/Ic4)=h-Ros/R4An(β6・Ic
1/Ic4)=h-Ros/R4(7nβ6+1nI
c 1/'IC4) (12).

Therefore, even in this case, by adjusting the resistor R4, the constant current I
If c 4 is I c 1 and the insertion resistor Ros is selected to be equal to the resistance value of the resistor R4, the offset voltage can be completely compensated.

In a range where the base input current of the transistor Q1 is small, that is, in a range where the collector current Ic1 is sufficiently small compared to Ic2, this circuit condition is satisfied in the normal operating range.
) If you select a transistor with a large current amplification rate, such as a transistor, and make its collector current a constant current, the offset voltage under this circuit condition will be equal to the current amplification rate β of transistor Q6.
6, the compensation is almost decisive, and at the same time the temperature characteristics are also effectively compensated.

That is, the compensation characteristics of offset voltage and temperature characteristics at a small input level are significantly improved.

The above explanation is based on the case where the constant currents Ic3, Ic5, and β6■c1 are each equal, but as already mentioned, it is also possible to design a circuit with approximately the same effect by appropriately selecting the ratio of these currents. .

FIG. 3 is an actual measurement diagram showing the improvement effect of the temperature compensation characteristic in the present invention, and shows the environmental temperature t'' (c) and the output pulse time width T.
a(ms) is expressed using the control terminal voltage v2M as a parameter.

In this experimental circuit, current amplification rate β is used as transistor Q6.
6 is approximately 100 pnp) transistors are used, and constant current ■c3. ■c, and β6■c1 are set so that the second term of formula 00) has a current ratio suitable for a negligible low input level, and formula (1)
Waveform human power pulse V1 and control steady voltage V expressed by
2 are respectively supplied from a common DC power supply vcc.

Therefore, it has been revealed that a particularly remarkable temperature compensation effect is exhibited in the lowest input level (Q group and relatively low (b) group region).

Monotonically increasing waveform pulse v1 as input as in this experimental circuit
If a circuit configuration is adopted in which the voltage v1. is generated from a common DC power supply Vcc, the voltage v1.
V2. Between vcc, cc V cc and V
Since the voltage relationship of 2ccVcc is always established, the time width Ta of the output pulse is completely unrelated to the DC power supply Vcc voltage fluctuation or change, as is clear from equation (9).

Therefore, the minimum operating voltage transformation value can be uniquely determined only from the circuit configuration, making circuit design extremely easy.

For example, if a pnp (pnp) transistor with a high current amplification rate is selected as the first stage transistor Q6 of circuit B, the circuit operating voltage will be VcEmintQ3 of transistor Q1.
It is determined by the sum of cEmin and VBEmin of Q6,
It is possible to design a circuit that operates satisfactorily with an extremely low power supply voltage of about 1.8V.

Furthermore, even if the current amplification factors of the transistors Q1 and Q2 constituting the differential amplifier are set high, the effects of the present invention will not be affected to the same extent. Therefore, an extremely high input impedance circuit can be realized, and the above-mentioned Together with the effect of improving temperature compensation characteristics, it is possible to easily design a circuit suitable for low-level input.

For example, the current c3 of a constant current power supply circuit is 10 μA, and circuit B
If the current amplification factor β1 of the transistor Q1 is selected to be 500 when the reversal current (2) is 3 μA, the effect of the present invention can be sufficiently exerted even for a waveform human input pulse v1 of 6 nA.

Furthermore, the minimum value of the steady voltage v2 applied to the control terminal 2 is vB Ern ] n of the transistor Q1 and V of the transistor Q3.
Since it can be lowered to the sum of cEmin, it has an extremely wide control range.

As explained in detail above, the present invention sufficiently compensates for the offset voltage of a transistor differential amplifier in terms of circuit and temperature, and facilitates circuit design such as lower voltage, higher input impedance, and integrated circuit. Since it is extremely easy to use, if it is applied to industrial fields such as time-limiting circuits, it can produce extremely remarkable technical effects.

[Brief explanation of drawings]

FIG. 1 is a main part configuration diagram showing an example of a known pulse duration control circuit using a transistor differential amplifier, and FIG. 2 is a connection circuit diagram of an embodiment of the present invention. Q2 and Q3 are transistors that constitute a known differential amplifier and transistor Q4'R4' that constitute a constant current power supply circuit, respectively; D2 and Ros are the inserted constant current circuit and resistor according to the present invention; Q5 and Q7 are respectively the above-mentioned transistors. This is a transistor inserted and set to a common base potential with transistor Q3. Further, FIG. 3 is an actual measurement diagram showing the improvement effect of the temperature compensation characteristics of the present invention.

Claims (1)

[Claims] 1 A differential amplifier including an input side transistor and a control side transistor whose emitters are commonly connected, a constant current power supply circuit connected to the common connection point of the emitters, and an electrically connected base of the input side transistor. A resistor Ro is connected to the connected pulse input terminal and the base of the control side transistor.
s, and a constant current circuit connected to a terminal on the control side transistor side of the resistor RO8, the constant current circuit being connected to the terminal of the resistor Ros on the control side transistor side. The constant current power supply circuit includes a first transistor whose collector is connected to a terminal on the control side transistor side, and a second transistor which is connected to the base of the first transistor and whose base and collector are short-circuited, and constitutes the constant current power supply circuit. The transistor and the second transistor have substantially the same electrical characteristics, so that the collector current of the first transistor is made constant in response to temperature changes in the output current of the constant current power supply circuit. An output pulse time width control circuit that receives a monotonically increasing waveform pulse as an input.