JPS63299401A - Cascade-connected amplifier - Google Patents

Abstract

PURPOSE:To sufficiently perform the temperature compensation of a first cascade connection circuit, by offsetting the change of an output current due to the temperature change of a collector cut-off current and the DC current amplification factor of the first cascade connection circuit with the temperature change of the collector cut-off current and the DC current amplification factor of a second cascade connection circuit. CONSTITUTION:The change component of a collector current due to the collector cut-off current ICBO1 of a first transistor 2 is offset by the change of the collector cut-off current ICBO3 of a third transistor 11. Similarly, the change component of the collector current of a second transistor 5 is offset by the change of the collector cut-off current ICBO4 of a fourth transistor 12, thereby, the change of the output current due to the currents ICBO1 and ICBO2 can be eliminated. Also, the change component of an emitter current due to the change of the DC current amplification factor h of the transistors 2 and 5 can be absorbed by the change component of the base currents of transistors 11 and 12. Therefore, the temperature compensation can be performed by eliminating the change of the output current due to the temperature change of the first cascade connection circuit 10 by the second cascade connection circuit 14.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to temperature compensation of cascaded amplifiers.

2. Description of the Related Art In general, a cascade-connected amplifier device is composed of a cascade-connected emitter-grounded transistor and a pace-grounded transistor, and performs signal amplification and direct current level shifting.

A conventional cascade-connected amplifier device will be explained based on FIG. Reference numeral 1 denotes a signal source, which is connected between the base of the first transistor 2 and the ground terminal 8. The emitter of the first transistor 2 is connected to a ground terminal 8 via an emitter resistor 4 and grounded, and the collector of the first transistor 2 is connected to the emitter of the second transistor 6. The pace of the second transistor 5 is connected to a stacked reference voltage terminal 6, and the collector of the second transistor 5 is connected to a power supply voltage terminal 9 via an output terminal 7 and a collector resistor 8. These first and second
Transistor 2.5. The emitter resistor 4 and the collector resistor 8 constitute a cascade connection circuit 10 .

With the above circuit configuration, the signal a from the signal source 1 is level-shifted from the ground level to the stacked reference voltage level input from the stacked reference voltage terminal 6, and from the output terminal 7 to the stacked reference voltage terminal 6 and the power supply voltage terminal 9. The signal is output to a DC amplifier (not shown) that operates at a voltage between 1 and 2 and undergoes signal processing.

Next, changes in the output current due to changes in the ambient temperature f will be explained. The first problem with the operation of a DC amplifier is that the DC operating point and gain change due to the heavy power supply pressure and the temperature dependence of the transistor. The temperature parameters of a transistor that change with respect to temperature F are mainly collector cut-off current (ICBO) - DC current increase factor (hFE) and pace-emitter voltage (VBE), and the general one is the temperature of ICBO and hFE. Changes in output current due to dependence are small compared to changes in output current due to temperature dependence of VBE and are often ignored.

FIG. 2 [Here, for VBE, the first transistor 2 receives a signal to the pace of the first transistor 2 via the transistor as described above (this is an amplifier with a common emitter and a PNP with a common collector). This can be compensated for by supplying a. As described above, the second transistor 5 is an amplifier using the first transistor 2 as a current source, and the change in output current due to the temperature dependence of VBE can be ignored.

However, in such a conventional configuration, there is a large level shift)! When high voltage is required and a cascade-connected amplifier is configured with high-voltage transistors, the temperature dependence of ICBO of the first and second transistors 2.5 is large, and furthermore, the temperature dependence of hFE is large. In addition, changes in the output current due to ICBO and hFE1 could not be ignored. For this reason, a method has been adopted in which the DC component of the level-shifted output is once cut, and then the DC component is regenerated to perform signal amplification.

The present invention solves the above-mentioned problems, and aims to provide a cascade-connected amplifier device that can compensate for changes in output current due to temperature dependence of ICBO and hFE with a simple configuration, and can directly amplify the output signal. It is something to do.

Means for Solving the Problems In order to solve the above problems, a first cascade connection circuit consisting of a first transistor and a second transistor that performs signal amplification and DC level shifting, a third transistor and a fourth transistor is provided. a second cascaded circuit consisting of transistors, connecting the emitter of the first transistor and the pace of the third transistor, connecting the emitter of the second transistor and the pace of the fourth transistor, and connecting the emitter of the first transistor and the pace of the fourth transistor;
The output current change due to a temperature change in the DC current amplification factor and collector cut-off current of the second cascade-connected circuit is canceled out by the temperature change in the DC current amplification factor and collector cut-off current of the second cascade-connected circuit. .

Operation According to the above configuration, the emitter of the first transistor and the pace of the third transistor are connected, and the emitter of the second transistor and the pace of the fourth transistor are connected. 3(7) The DC flJfa rate and the cut-off current of the l-transistor are the same, the DC amplification factor and the collector cut-off current of the second transistor and the fourth transistor are the same, and the first transistor By making the DC operating currents of the cascaded circuit and the second cascaded circuit the same, the temperature of the first cascaded circuit is sufficiently compensated.

EXAMPLE Hereinafter, an example of the present invention will be described based on the drawings. Components and circuits that are the same as those in FIG. 2 showing the conventional example are given the same reference numerals and explanations thereof will be omitted.

FIG. 1 shows a circuit diagram of a cascade-connected amplifier according to the present invention. FIG. 1 shows a conventional example in which a second cascade connection circuit 145 consisting of a third transistor 11, a fourth transistor 12, and a second emitter resistor 18 is connected to the first cascade connection circuit 10 of FIG. It's a great thing. The third transistor 11 is the same IC as the first transistor 2.
BO, hFE, has the characteristics of collector loss, the pace of the third transistor 11 is connected to the emitter of the first transistor 2, and the emitter of the third transistor 11 is connected to the ground terminal through the second emitter resistor 18. 8, and the collector of the third transistor 11 is connected to the emitter of the fourth transistor 12. The fourth transistor 12 is the same IC as the second transistor 5.
B.O.

hFE has the characteristic of collector loss, the base of the fourth transistor 12 is connected to the emitter of the second transistor 5, and the collector of the fourth transistor 12 is connected to the power supply voltage terminal 9. Furthermore, the DC operating current of the second cascade connection circuit 14 is substantially the same as that of the conventional first cascade connection circuit 10.

In the above configuration, if the ambient temperature changes now, the first.
The ICBO and hFE of the second transistor 2.5 change, the output current flowing through the collector resistor 8 changes, and the DC voltage at the output terminal 7 changes. The pace of the fourth transistor 11 operating under the same conditions as the second transistor 5 and the emitter of the second transistor 5 are connected. Therefore, the change in collector current due to the collector cut-off current I CBOI of the first transistor 2 is the collector cut-off current I CBO3 of the third transistor 11.
is canceled by the change in the amount of injection into the emitter of the first transistor 2, and the change in the collector current of the second transistor 5 due to the collector cut-off current ICBO2 of the second transistor 5 is the collector cut-off current of the fourth transistor 12. The changes in the amount of injection into the emitter of the second transistor 5 of the ICBO 4 are thus canceled out. The change in output current due to IC801%ICBO2 of the second transistor is eliminated. Further, the change in the emitter current of the first and second transistors 2.5 due to the change in hFE of the 1.degree. second transistor 2.5 is the 3.degree. Fourth transistor 11
, 12 pace current changes, and the 1st. Second
The change in output current due to hFE of transistor 2.5 is eliminated.

In this way, a change in the output current due to a temperature change in the first cascade connection circuit 10 causes a change in the output current in the second cascade connection circuit 14.
temperature compensation is performed.

Effects of the Invention As described above, according to the present invention, the DC operating current of the first cascade connection circuit and the second cascade connection circuit, the collector cutoff current of the transistors constituting both cascade connection circuits, and the DC current amplification factor are the same. and L, since the emitter of the transistor in the first cascade connection circuit and the pace of the transistor in the second cascade connection circuit are connected, the output current due to temperature changes in the collector cutoff current and DC current amplification factor of the first cascade connection circuit is This change is offset by the temperature change in the collector cutoff current and the DC current amplification factor of the second cascade connection circuit, and the first cascade connection circuit can be sufficiently compensated for the temperature.

Therefore, it is possible to realize a DC amplifier that can directly amplify the output signal, which has great practical value.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a cascade-connected amplifier showing an embodiment of the present invention, and FIG. 2 is a circuit diagram of a conventional cascade-connected amplifier. 2...First transistor, 5...Second transistor, 10...First cascade connection circuit%11.
. . . third transistor, 12 . . . fourth transistor, 14 . . . second cascade connection circuit.

Claims (1)

[Claims] 1. A first cascade connection circuit consisting of a first transistor and a second transistor that performs signal amplification and DC level shifting, and a second cascade connection circuit consisting of a third transistor and a fourth transistor, 1st
connect the emitter of the second transistor and the third transistor, and connect the emitter of the second transistor and the fourth transistor.
By connecting the paces of the transistors, the output current change due to temperature change in the DC current amplification factor and collector cut-off current of the first cascade connection circuit is expressed as the DC current amplification factor and collector cut-off current of the second cascade connection circuit. A cascaded amplifier configured to be canceled by temperature changes.