JPS62115901A - Amplifier - Google Patents

Abstract

PURPOSE:To make an amplifier into ICs by connecting a dummy load to the collectors of the 1st and 2nd transistors, negatively feeding back an output supplied to said load to a drive amplifier, and connecting the load to the collectors of the 3rd and fourth transistors. CONSTITUTION:The collectors of the transistors Q7 and Q8 and the emitters of transistors Q9 and Q10 are connected to the bases of transistors Q9 and Q10 with reverse polarities and positive and negative power source terminals T2 and T3, respectively. The emitters of the transistors Q7 and Q8 and the collectors of the transistors Q9 and Q10 are connected to some end of a dummy load resistance R0 and the base of a transistors Q2. When a sound signal is supplied to a terminal T1, it is sequentially current-amplified by transistors Q1-Q10 and supplied to the resistance R0. However, in this case, a 100% negative feedback is applied, and the gain of an amplifier, viewing from the resistance R0, is the same. At that time, since the transistors Q9 and Q10 employ the resistance R0 as a load, oscillation never occurs even if a large amount of negative feedbacks are applied. Thus capacitors C2 and C3 for a high frequency compensation and a capacitor C1 for negative feedback are made unnecessary, thereby facilitating to make the amplifier into ICs.

Description

DETAILED DESCRIPTION OF THE INVENTION A low frequency amplifier such as a radio receiver is configured as shown in FIG. 1, for example.

That is, transistors QL and Q2 constitute a differential amplifier, and transistors Q3 . Q4 is connected to form the front stage. Further, the transistor Q5 is used for driving, and a constant current source transistor Q6 is connected to its collector, so that the DC portion of the collector current of the transistor Q5 is absorbed into the transistor Q1. Furthermore, the transistor Qv,
Qs is push-pull connected to form an output stage.

Therefore, when an audio signal is supplied to the input terminal TL, it is converted into a current by the transistor Ql, and thereafter, the current is sequentially amplified and then supplied to the speaker SP.

Incidentally, in such an amplifier, elements R1, R2, and C are used to stabilize DC operation and reduce distortion.
A negative feedback I of 60 to 70 dB must be applied depending on t. However, in this case, the impedance of the speaker SP changes greatly depending on the frequency, from inductive to octagonal, so when applying such a large amount of negative feedback, high-frequency compensation must be performed using elements C2, C3, and R3. It won't happen.

However, if capacitors 01 to C3 are required for negative feedback and high-frequency compensation, the number of bins and external peripheral components will increase when converting this amplifier into an IC, which is disadvantageous to IC conversion. At the same time, the effect of converting to fc becomes smaller.

In view of these points, the present invention provides capacitor 01
This is an attempt to provide an amplifier that does not require C3.

Let's explain one example below.

In FIG. 2, transistors Q1 to Q8 are connected in the same way as the amplifier in FIG.
transistors Q9.a whose collectors have opposite polarities; Q+
o, and these transistors Qs, Q
+o emitters are connected to positive and negative power supply terminals T2 and T]. Furthermore, transistor Q? , Qe and the collectors of transistors Q9 and QIO are connected to one end of a pseudo load resistor Ro and to the base of transistor Q2. Note that a base bias is supplied to the transistor Q1 through a resistor R4.

Furthermore, the bases and emitters of transistors Q9n and QYJn are connected in parallel between the bases and emitters of transistors Qs and Q+o, and these transistors Q3n and
The collectors of Q and n are connected to one end of speaker sp.

In this case, when the corresponding transistors are assumed to have the same characteristics and the same base-emitter voltage is supplied, the collector currents of the transistors Q, n, Q, n are equal to n of the collector currents of the transistors Qs, Q+o. (n>1), that is, a nil similar transistor. Further, the above elements, especially the transistors, are made into a (1) chip IC.

According to such a configuration, when an audio signal is supplied to the terminal T1, this signal is sequentially current-amplified by the transistors Q1 to Q+o and supplied to the resistor Ro. However, in this case, the collectors of transistors Q9 and Q+o are directly connected to the base of transistor Q2, so
100% negative feedback will be applied, and the resistance 'et R
The gain of the amplifier seen from o is 1x.

However, transistors Q9n and QlcIn are supplied with a base current n times that of transistors Q9 and Q+o, so transistors Q, n, Q, and n are supplied with a base current of 1-transistor Q9. A collector current of n times Q, , flows, and therefore,
The gain A of the amplifier seen from the speaker SP is the speaker SP
Assuming that the impedance of is Rst', an amplified output is thus supplied to the speaker SP. The negative feedback of (・ransistor Q9
．． QIO and at this time, transistor Q9. Since Qlll is loaded with the resistor WRo, oscillation does not occur even if such a large amount of negative feedback is applied, and therefore, the capacitors C2 and C3 for high frequency compensation are not required. Further, the capacitor C1 for negative feedback is also unnecessary. Therefore, it is easy to use an IC, and the effect of using an IC is large.

Note that for the same base-emitter voltage, the collector currents of transistors Q3n, Q, n are changed to transistors Q9, . To make it n times Q+*, transistor Q3n
The junction area or peripheral length of the emitter junction of , Qw3n may be n times that of the transistor Q s +Q 11). Furthermore, as shown in Figure 3 or Figure 4,
n equal current amplification factors hFI! The collector current can be increased by n times by connecting two transistors in parallel, and the characteristics can also be made uniform by using an emitter resistor or a base resistor.

[Brief explanation of drawings]

FIG. 1 is a connection diagram showing an example of an amplifier, FIG. 2 is a connection diagram of an example of the present invention, and FIGS. 3 and 4 are connection diagrams of some examples thereof. T1 is an input terminal, and sr is a speaker.

Claims (1)

[Claims] A drive amplifier, first and second transistors with opposite polarities, and third and fourth transistors with opposite polarities that output a collector current n times (n>1) that of the first and second transistors. and a pseudo load, the collectors of the first and second transistors are connected to each other to form a series circuit, and this series circuit is connected to a DC power source, and the third and fourth transistors are connected to each other to form a series circuit. The collectors of the transistors are connected to each other to form a series circuit, and this series circuit is connected to a DC power supply, and drive outputs having opposite phases to each other are taken out from the drive amplifier to output the drive outputs of the first and third transistors. is supplied to the base and the bases of the second and fourth transistors;
The pseudo load is connected to the collector of the second transistor, the output supplied to the pseudo load is negatively fed back to the drive amplifier, and the load is connected to the collectors of the third and fourth transistors. Amplifier.