JPH0486111A - Amplifier circuit - Google Patents

Abstract

PURPOSE:To attain constant voltage control to the amplifier circuit to a desired value with an excellent constant voltage characteristic by employing a transistor(TR) which receives a connecting point potential of a series resistance circuit to its base for a constant voltage circuit. CONSTITUTION:When the resistance of resistors R1, R2 of a base bias circuit comprising the resistors R1, R2 and transistors(TRs) Q1, Q2 is set as R1=R2, a collector-emitter voltage of the TR Q2 is made constant. Similarly, when the resistance of resistors R4, R5 of a constant voltage circuit comprising the resistors R4, R5 and a TR Q7 is set as R4=R5 t a collector-emitter voltage VCE of the TR Q7, that is, a base-base voltage between an NPN TR Q5 and a PNP TR Q6 is controlled to be a constant voltage. The constant voltage characteristic is revised optionally by revising the resistance of the resistors R4, R5 while the ratio is kept constant.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to an amplifier circuit with improved crimp operation characteristics in a high frequency region.

(B) Prior Art A conventional single-ended amplifier circuit (hereinafter simply referred to as an amplifier circuit) will be explained with reference to FIG.

This amplifier circuit has a power supply terminal +VCC and an output terminal ■. 0□, an NPN transistor lid 17 whose collector and emitter are connected to each other, a power supply terminal -■co, and an output terminal V.

PN whose emitter and collector are connected to lJ□ respectively
P transistor Q +a and NPN to obtain a predetermined current amplification factor) NP connected Darlington to the range shifter Q +7, PNP) range shifter Q 18, respectively
N) lunge lid Q +s, PNP) lunge lid Q
16, resistor R18, R+o and transistor Q l
3 base bias circuit and transistor Q
A differential amplifier circuit consisting of l l, Q1□, and resistor R24
, a negative feedback circuit including a capacitor CI4, etc.

The base bias circuit consisting of resistors R18, Rlg and transistor Q13 is configured such that the resistance values of resistors R18 and R are set to, for example, R16-3R4, and the collector-emitter voltage VcE of transistor Q11 is constant Vcff=V, g (R+++R12)/R=4■ll□
#2.4V (VeE is the base-emitter voltage of transistor Q I+) Therefore, if we focus on the potentials at points A and B, the potentials ■6, ■8
The relationship is V A = V B + 4 V a , and the base-emitter voltage of all transistors is vag
Assuming that the potential ■8 is equal to Va-2Veh, that is, V, = V B+ 4 V 82" 2 V !I
When E, NPN transistor lid 1, Q l 7, P
NP) All transistors of the range shifter Q+a and Q18 are turned off.

Potential V a V s > 2 V a E
, the PNP) lunge cover Q re and Q18 are turned off, and the potential vA = V B +4 V BE > 2 V
NPN by IIE) lunge lid Q15 and Q17
is the positive polarity V determined by the constant of the negative feedback circuit, )1.
Outputs 7.

Also, when the potential ■8≦V a<2 V ue, the NPN transistor lid 5 and Q+7 are turned off, and the PNP
Transistors Q16 and Q18 operate to output VO, )7 with a predetermined amplitude of negative polarity.

As described above, the single-ended push-pull amplifier circuit has N
PN) lunge lid Q15 and Q17, PNP) lunge lid Q16 and Qto operate alternately and VOLI□
Output.

FIG. 4 is a diagram of actually measured waveforms when the output stage transistor of the amplifier circuit described above is operated at high bias and 30KH2.
) Emitter current IE11 of lunge lid Q18. IEl
The waveform of VBH and its base-to-base voltage VBH are shown.

When NPN transistor Q 14 and PNP transistor Q 15 are operated at high bias, excessive minority carriers are accumulated in the base regions of these transistors.

Therefore, the NPN transistor lid +5, Q is clipped (
For a while after coming out of the saturated state, a current rEa′ flows in a superimposed manner based on the minority carriers, and the output V.Uo maintains the level of the saturated state.

This output■. U□ is connected to transistors Q +l, Q
When input to the inverting input terminal of the differential amplifier circuit consisting of Q12, the transistor Q12 of the differential amplifier circuit is turned off, thereby further biasing the transistor Q12 whose bias has begun to change relatively deeply. become. Then, the transistor Q I+ turns on and PNP )
Run shifter Q +a and Q 18 are turned on and NPN based on excess minority carrier) Run shifter Q 17 to PN
A current flows through the P transistor Q IA. At this time, the excess minority carriers are accelerated by the power supply voltage 2Vcc, so the current becomes extremely large, resulting in large power loss.

It should be noted that there are other possible causes of the current flowing from the NPN transistor cover Q 17 to the PNP transistor cover 8, but these will be reserved because they include some unexplained parts.

(c) Problems to be Solved by the Invention Therefore, the general problem to be solved by the present invention is that when an amplifier circuit is clipped at a high frequency, the base-to-base voltage VBB of a transistor that is connected in a single-ended push-pull manner is This invention is based on the discovery of the phenomenon in which The amplifier circuit studied during the development process of the present invention will be explained with reference to FIG.

The amplifier circuit shown in the same figure is shown in FIG.
N) Lunge lid Q17 and PNP transistor lid +
A Zener diode ZD is added between the base of a, and NPN) transistor Q17 and P
NP) Base to pace voltage v of lunge lid Q18
Since s8 is controlled at a constant voltage by a Zener diode ZD with a breakdown voltage of about 2V, in principle it is an NPN
Transistor Q17 and PNP transistor Q18
This prevents both transistors from turning on at the same time, thus achieving the intended purpose.

However, the breakdown characteristics of the Zener diode ZD having a breakdown voltage of about 2V are dominated by Zener breakdown, and since the breakdown characteristics are smooth, it is extremely difficult to obtain the required constant voltage characteristics. Furthermore, due to the smooth breakdown characteristics and the influence of contact resistance drop of the Zener diode ZD, there is a problem that the Zener diode ZD operates linearly in the breakdown region, making it impossible to completely control the base-base voltage VBB at a constant voltage. ing.

Therefore, the more specific problem to be solved by the present invention is to control the base-to-base voltage (88) of a single-ended push-pull connected transistor to a desired value with good constant voltage characteristics. The object of the present invention is to provide an amplifier circuit that can easily prevent thermal runaway.

(Fc Means for Solving the Problems) The present invention has been made in view of the above-mentioned problems, and is intended to control the voltage between the bases of the output stage transistors connected in a single-ended push-pull manner and to control the constant voltage characteristics. By inserting a simple constant voltage circuit, a pulse-like rise in the base-base voltage can be suppressed and a through current in the output stage transistor can be prevented.

(4) As the constant voltage circuit uses a transistor whose base input is the connection point potential of the series resistor circuit, voltage control can be easily set by the resistance ratio of the series resistor circuit, and constant voltage characteristics can be easily set by the resistance value. It becomes possible to set criticality. Furthermore, since settings can be made by adjusting the resistance, adjustments can be made after assembly, making it particularly suitable for hybrid integration.

(f) Example An embodiment of the present invention will be described with reference to FIG.

The amplifier circuit shown in the figure has a power supply terminal of 10V. C and output terminal V. N with collector and emitter connected to U□, respectively
PN) Lunge lid Q5, power supply terminal - VCC and output terminal■
. 1. A PNP transistor Q6 whose emitter and collector are connected to l
The circuit is composed of a base bias circuit consisting of an NPN transistor lid, a PNP transistor lid, resistors R5, R2, and transistors Q1, Q2, and a constant voltage circuit consisting of resistors R4, R5, and a transistor Q7, which are connected to each other by Darlington. Note that some voltage amplification circuits and negative feedback circuits are omitted.

Although the present invention is not limited to an amplifier circuit formed into a hybrid integrated circuit, in the embodiment, the transistor is mounted in a chip shape on a wiring pattern formed on an insulated metal substrate, and the resistor is a chip resistor or a printed circuit. The base bias circuit and the constant voltage circuit are also mounted on a wiring pattern formed on an insulated metal substrate using a resistor (not shown).
1, PNP) is placed adjacent to the lunge lid Q6 to quickly detect its temperature and appropriately compensate for the temperature of the amplifier circuit.

The resistance values of resistors R1 and R2 of the base bias circuit consisting of resistors R1 and R2 and transistors Q1 and Q2 are R,
= R2, and the collector-emitter voltage of transistor Q2. E is a constant VCE-2VBE (R1+R
2) /R2Vag (Vac is the base-emitter voltage of transistor Q, Q2) Therefore, the relationship between input signal ■1 ° and VIN is V +
= V r N + 4 V BE, and the conventional example A
, B are obtained, and the same operation as a conventional amplifier circuit is performed.

In exactly the same way, the resistance values of resistors R1 and R6 of the constant voltage circuit consisting of resistors R4 and R5 and transistor Q7 are approximately R, = R6
The collector-emitter voltage of transistor Q7 is set to . E, i.e. NPN) lunge lid Q5, P
NP) The base-to-base voltage V@8 of the lunge cover Q6 is VCE=V8B=VBE (Ra + Rs)/R5=2V
,.

The voltage is controlled to a constant voltage. The temperature characteristics of this constant voltage circuit are the same as the temperature characteristics of the base-emitter voltage of transistor Q7, and are similar to the temperature characteristics of output stage transistors Q5 and Q6. Compensation 6 can be done. Further, this constant voltage characteristic can be arbitrarily changed by changing the value while keeping the ratio of the resistance values of the resistors R4 and R5 fixed.

Figure 2 shows that the ratio of the resistance values of resistors R4 and R6 of the constant voltage circuit is set to 1, and the resistance values are changed to 75Ω, 330Ω, and 3Ω.
An example of the frequency vs. total current characteristics of the amplifier circuit when It has been shown that the amplifier circuit tends to go into thermal runaway as the temperature increases. In addition, for C distortion, resistance R4,
When R5 is set to 75Ω and 330Ω, stable operation is achieved up to a frequency of about 100KH, and the circuit current shows a remarkable tendency to decrease as the operating frequency increases.

Note that the above-mentioned resistance value should be changed along with the rated output of the amplifier circuit, and also changes depending on the specification of the transistor Q7 of the constant voltage circuit.

([) Effects of the Invention As described above, according to the present invention, a constant voltage circuit using a transistor that inputs a resistor-divided voltage to the base is connected between the bases of the output stage transistors connected in a single-ended bundling manner. In addition, the voltage can be controlled by the ratio of resistance values, and the constant voltage characteristics can be changed by changing the specifications and resistance values of the transistors constituting the constant voltage circuit.

Therefore, the present invention can easily improve the clipping operation characteristics in the high frequency region for any standard amplifier circuit.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of a main part of an embodiment of the present invention, Fig. 2 is a frequency-circuit current characteristic diagram of the embodiment, Fig. 3 is a circuit diagram of a conventional amplifier circuit, and Fig. 4 is a conventional amplifier circuit. Operation waveform diagram, 5th
The figure is a circuit diagram of the main parts of another conventional amplifier circuit. No. I R4 Q1-Q, - Transistor, R2-R7 resistance, V
IN, V IN″・Input terminal, ■.0□・Output terminal. Fig. 2

Claims (5)

[Claims] (1) A third transistor is connected between the bases of the first and second transistors connected in a single-ended push-pull manner.
An amplifier circuit characterized in that the collector and emitter of the transistor are connected to each other, a series resistance circuit is connected between the collector and the emitter, and the potential at the connection point of the series resistance circuit is inputted to the base of the third transistor. . (2) The amplifier circuit according to claim 1, wherein the resistance value of the resistor and the ratio thereof are set so that the voltage between the collector and emitter of the third transistor is clipped at approximately 2V. (3) The amplifier circuit according to claim 1, wherein circuit elements constituting the amplifier circuit including the first to third transistors and resistors are mounted on an insulated metal substrate. (4) The amplifier circuit according to claim 1, wherein the third transistor is arranged adjacent to the first and second transistors. (5) The amplifier circuit according to claim 1, wherein the first and second transistors are complementary transistors.