JPS5918882B2 - transistor warmer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION There is a transistor circuit shown in FIG. 1 that can be used as a gain leg circuit or a switching circuit.

That is, in the circuit of FIG. 1, the input signal is differentially amplified and taken out by the transistor Qat Qb. At this time, when the base voltage Va of the transistor Qc is changed, its collector current Io is changed and the transistor Qa , Qb changes, this changes the current amplification factors of the transistors Qa, Qb, and their gains change, so that gain control, switching, etc. can be performed.

However, in this circuit, the DC level Vo of the output signal is Vo = Vcc − I ORL, so if the collector current Io is controlled by changing the base voltage Va, the DC level Vo of the output signal will change. .

This also changes the dynamic range on the output side.

Furthermore, due to a change in the collector current Io, the transistor Qa
, Qb changes, their base-emitter voltages change, which also changes the dynamic range on the input side.

Also, the collector current Io & ζ is the total current consumption, but if the current consumption changes in this way, if it is integrated into an IC, it may cause a change in the voltage drop in the internal conductive pattern and cause interference with other circuits. , which is disadvantageous for IC implementation.

Therefore, the present invention aims to eliminate these drawbacks.

Now, considering the internal impedance of a diode, it is determined by the current flowing through the diode, and its value Rd is given by the following equation and is shown as in FIG. 2A.

6 RdCΩ]-□ IdCmA] ■d: Diode current Therefore, by using a diode as a variable impedance element, a gain control circuit etc. can be constructed, but with a simple diode, when a signal voltage, that is, an AC voltage is applied to it, Distortion occurs due to nonlinearity.

Therefore, as shown in FIG. 3, a diode Da is connected.

Consider the case where Db is connected in series and a current is passed through it by a sink type constant current source Xa.

Then, the impedance Rab of the series circuit of the diodes Da and Db becomes the sum of the impedances Ra and Rb of the diodes Da and Db, Rab=Ra+Rb, as shown in FIG. 2B.

That is, since the diodes Da and Db operate in a complementary manner, linearity is improved, and therefore, even when an AC voltage is applied for the first time, distortion is less likely to occur.

The present invention focuses on such points and performs gain control, etc., and an example thereof will be explained below.

In FIG. 4, transistor Q1. The emitter of Q2 is
The transistor Q5 is grounded between its collector and emitter, and the bias power supply V is connected to the base of the transistor Q5.
is connected, and the base of transistor Q1 is connected to input terminal T3.
, the base of transistor Q2 is connected to bias power supply V2, and transistors Q1 . The collector of Q2 is connected to the output terminal T1. The first differential amplifier 1 is configured by being connected to the power supply terminal T2 and to the power supply terminal T4 through a load resistor R1°R2 (R1'-R2).

and transistor Q1. A diode D1.Q2 is connected as a variable impedance element between the collectors of D1. D2 are connected in series with opposite polarities.

The transistors Q3 and Q4 constitute the second differential amplifier 2, and the emitters of the transistors Qs and Q4 are grounded through the collector and emitter of the transistor Q6, and the bias power supply v6 is connected to the base of the transistor Q6. , the base of transistor Q3 is connected to bias power supply V3, and its collector is connected to transistor Q3.
r is connected to the emitter of Q2, the base of transistor Q4 is connected to a control voltage source V4, and its collector is
It is connected to the connection point between diodes D1 and D2.

In this case, the collector current of transistor Q5 is
For example, it is made sufficiently larger than the collector current of transistor Q3.

According to such a configuration, when an input signal (including the bias voltage of the transistor Q1) is supplied to the terminal T3, the input signal is supplied to the terminal T3. Q2 differentially amplifies the terminal T1. It is taken out at T2.

In this case, if the control voltage V4 is changed to change the collector current of the transistor Q4, this will also change the current flowing through the diodes DI and D2, so the impedance of the series circuit of the diodes DI > D2 will change. do.

When the control voltage v4 is increased, a sufficient current flows through the diode Di2D2, its series impedance becomes sufficiently small (turned on), and the output signal is transmitted through the transistors Q1. Since the output signals are obtained at the collectors of Q2 at opposite phase levels, this output signal is connected to the diode DI.
, D2, and thus the terminals T1. No output signal is obtained at T2.

That is, the gain is minimum.

On the other hand, when the control voltage V4 is made small, the current flowing through the diode DI7D2 becomes O, and its series impedance becomes sufficiently thick ((off)), so the output signals of the transistors Ql and Q2 are canceled out. The gain is taken out as it is to the terminals T1 and T2, that is, the maximum gain is obtained.

Therefore, the gain can be controlled by changing the control voltage v4.

That is, if the series impedance of the diode DjD2 is 2Rd, this circuit can be shown as shown in FIG. 5A under equal constraints, and furthermore, this equivalent circuit can be transformed as shown in FIG. 5B.

However, since the connection point of R3, -R23=R1Rd/(R1+Rd) and the impedances R12, R23, and R3□ is an AC zero potential point, the transistors Ql, Q
The emitter resistance of 2 is r.

Then, the voltage gain Av of this circuit is A7 = 5 rods.

- Average RdA. [Double] ro re (R1+Rd) becomes.

However, Ao is the voltage gain without negative feedback.

Therefore, if the series impedance of the diodes DI and D2 at the minimum gain is 2Ro, the minimum first gain Am1n is RtRoA.

Am1n': 20 log CdB
]re(R1+Ro).

Also, the diode DI at maximum gain? If the series impedance of D2 is infinite, the maximum gain Amax is RlA.

Amax’: 20 log-[dB] e becomes.

The difference between the minimum gain Am1n and the maximum gain Amax, that is, the gain width ΔAv is R1+R.

ΔAv=Amax−Amin=20 log−
[dB]R0.

Thus, according to the present invention, gain control can be performed.

And in this case, in particular, according to the invention, there is no drawback as with the circuit of FIG.

That is, since the pair of diodes Di j D2 are used as variable impedance elements, less distortion occurs, as explained with reference to FIG. 2B.

When the control voltage V4 is further changed, the transistor Qs
, Q4's collector current changes, but these changes in collector current are complementary, and of the collector current (DC component) of transistor Q3, the current flowing to resistor R1 through transistor Q1 and the current flowing to resistor R1 through transistor Q2 are complementary. The currents flowing through R2 are equal to each other, and further,
Of the collector current of transistor Q4, diode D
The current flowing through resistor R1 through diode D2 and the current flowing through resistor R2 through diode D2 are equal to each other.

Therefore, since the current flowing through the resistor R1 and the current flowing through the resistor R2 are equal and constant, the control voltage V
4, even if terminal T1. The DC levels of T2 are constant and equal to each other.

Furthermore, even if the control voltage V4 is changed, the transistor Q1. The dynamic range on the output side of Q2 rarely changes.

Furthermore, transistor Q1. Since the collector current of transistor Q5 (ItL) is flowing through Q2, the control voltage V4
Even if the collector current of transistor Q3 changes due to a change in transistor Q1. The base-emitter voltage of transistor Q2 is approximately constant, so that transistor Q1. Q
The dynamic range on the input side of No. 2 hardly changes.

Also, the total current consumption of this circuit &ζ transistor Q5,
Since it is equal to the sum of the collector currents of Qa and is always constant, it will not cause any inconvenience when integrated into an IC.

In the example of FIG. 6, the diode DI? This is a case where a parallel circuit of transistors Q7 and Qg is used instead of the series circuit of D2.

According to this circuit, since the transistor Q4 only needs to control the base current of the transistors Q7 and Qs, the collector current of the transistor Q6 can be made sufficiently small, and the circuit efficiency is improved.

Furthermore, in the example of FIG. 7, a transistor Q+t t Ql□ is connected in place of the resistors R, , R2, and
Transistor Q1. This is the case when a resistor R3 is connected in parallel to the diode Di) D2 as a load for Q2.

and transistor Qu, Q12 and transistor Q1
3' constitutes a first current mirror circuit, and a base bias is applied to transistors Q1□ and Q1□, and transistors Q5, Qe and transistor Q14
A second current mirror circuit is constructed, and base bias is applied to transistors Q5 and Qa.

Further, in order to make the collector currents of the transistors Q5 and Qa equal to each other, it is sufficient to set, for example, R,=R5=R6.

In this circuit, if -R3 is substituted for the resistors R1 and R2, the above-mentioned equations hold true.

Furthermore, in the example of FIG. 8, the resistor R3 of FIG. 7 is configured as a series circuit of resistors R31 and R3□ (R31=R32), and the bias power supply v7 is connected to the midpoint of their connection. be.

Therefore, in this circuit, terminals T1. The DC level of T2 is V
7.

In addition, in the example of FIG. 9, the resistor R7t R8 (R7
=R8) is connected.

Therefore, in this circuit, (R10R7) (R1+RO) ΔAv=20 log Cd
B](R1+R7)Ro+RIR7, and the control width ΔAv of gain control can be made small.

In the above description, the circuit of the present invention has been described as a gain control circuit, but the signal supplied to the terminal T3 and the signal supplied to the base of the transistor Q4 (base voltage V4)
By changing the form of the circuit, it can be operated as a switching circuit, a mixing circuit, a modulation circuit, a multiplication circuit, etc.

[Brief Description of the Drawings] Fig. 1 is a connection diagram of a conventional example, Figs. 2 and 3 are characteristic diagrams and connection diagrams for explaining the present invention, Fig. 4 is a connection diagram of an example of the present invention, FIG. 5 is an equivalent circuit diagram thereof, and FIGS. 6 to 9 are connection diagrams of other examples of the present invention. T1. T2 is an output terminal, and T3 is an input terminal.

Claims (1)

[Claims] 1 Emitters of the first and second transistors are connected to collectors of a third transistor, collectors of the first and second transistors are connected to a power supply through loads, respectively, and collectors of the first and second transistors are connected to a power supply through loads, and In between, a pair of variable impedance elements are connected with opposite polarities to each other, and connect the emitter of the third transistor and the fourth transistor.
The emitter of the transistor is connected to a constant current source, the collector of the fourth transistor is connected to the pair of variable impedance elements, and a fifth transistor is connected between the emitters of the first and second transistors and ground. The collector and emitter of the transistor are connected, a bias source is connected to the base of the fifth transistor, and the first and second transistors are connected to each other.
A first signal is supplied to one base of the transistor, a second signal is supplied to one base of the third and fourth transistors, and a collector of at least one of the first and second transistors. A transistor circuit from which an output signal is taken.