SU1506514A1 - Amplifier - Google Patents

Abstract

The invention relates to radio engineering. The purpose of the invention is to increase the load capacity in the large signal mode. The amplifier contains an input differential cascade 1, a pre-output differential cascade 2, an unbalanced load, performed on a current reflector 3, resistors 4, 5, a current source 6, performed on transistors 7, 8 and a resistor 9, an output emitter follower (EP), performed on a transistor 10 and the current-carrying element made on the transistor 11. The output EA on a large signal operates in a push-pull mode, in which the value of the output current when transmitting signals of both polarities is much higher than the initial bias current of this helmet a, and this is determined by a high load capacity of the amplifier when operating in the capacitive load. At the same time, the output ES has the stability of the initial mode and does not affect in any way the own small signal characteristics of the differential stages 1 and 2. 3 sludge.

Description

Fi.g.1

The invention relates to radio and technology and can be used

as part of operational amplifiers and other amplifying circuits.

The purpose of the invention is to increase the load capacity in the large signal mode.

fia FIG. 1-3 shows the electrical circuit of the amplifier.

The amplifier contains an input differential cascade 1, a pre-output differential cascade 2, an unbalanced load, filled on a current reflector 3, resistors A and 5, a current source 6, made on transistors 7 and 8, an additional resistor 9, an output emitter follower, executed on a transistor 10, the current-carrying element executed on the additional transistor 1 1.

The amplifier works as follows.

Provided that there is no signal at the amplifier inputs, the voltage drop across resistors 4 and 5 is equal to

„T, n.U, 67-R5 4 - 5 - R9 R9

where i r my fall voltage e

base-emitter junction

transistor 7.

If you choose the resistance of these resistors so that R9 / R4 R9 / R5 p, then Uc Uj Therefore, if transistors 7 and 11 are matched and with equal geometric dimensions, then their collector currents will be the same and equal to Ij. In general, the initial collector current of the transistor 11

I

CM

rq (R6-n-R3) Iol exp J,

where Ijj is the bias current of the input stage 1 (output current of the current source); q is the electron charge;

K is the Boltzmann constant; T is the Kelvin temperature. Therefore, the proposed technical solution allows for a strict certainty and stability of the initial bias of the output emitter follower. ) When transmitting a variable signal on a positive half-wave of the increment — output t shackles of the pre-exit

1506514.

differential stage 1 is + D1, so the emitter follower output current is

you

2ui B,

where B is the current gain

emitter follower. When transmitting a negative half-wave signal, a positive increment of the output current of the pre-output differential stage 2 + is fed to the input of the current reflector 3, while a current 2D1 flows through the resistors 4, 5. At the base-emitter junction of the transistor 11, the voltage increases by the value of uU 2ui R4-R5 / (R4 + R5) or when, di. In this case, the collector current of the transistor 11 and, accordingly, the output current of the amplifier are

five

0

five

0

exp

ii5-ia

 8Ы jj-p

Consequently, the output emitter follower amplifier formed by transistors 10 and 11, on a large signal, operates in a push-pull mode, in which the output current when transmitting signals of both polarities greatly exceeds the initial bias current of this stage, which determines the high load capacity of the amplifier when working on capacitive load. At the same time, the output emitter follower possesses the stability of the initial mode and does not affect in any way the own small signal characteristics of the input and pre-output differential stages 1 and 2.

Similar characteristics at low frequencies are variants of the proposed amplifier, partially shown in FIG. 2, 3. However, the option

5, a fragment of which is shown in FIG. 2 has an internal positive feedback through the capacitor. The collector is the base of the transistor 11. In another embodiment, through the collector capacitance. The base of the transistor 11 closes the intra-stage negative feedback circuit. The presence of such links is significantly reflected in the intrinsic frequency response of the amplifier,

Claims (1)

5 which may be useful for some special applications. Invention Formula Amplifier containing input connected in series and pred10 5 15065 output differential cascades and output emitter follower, while the input differential cascade is complete on transistors of one type, a current source included in the common emitter circuit of transistors, in whose collector circuits a symmetrical load is included, a pre-output differential cascade performed on transistors of another type, in collector circuits which included an asymmetrical load, made in the form of a current reflector, the output of which is the output of the pre-output differential stage, and in the emitt The black circuits of the current reflector transistors included the corresponding resistors, the output emitter follower. performed on a transistor, named the type of transistors of the input differential cascade and current reflector connected according to the circuit with common collector and in the emitter circuit of which the current-giving element is included, is dissimilar, since in order to increase the load capacity in the large signal, is15 20 25 0 65 five 0 five 146 The current volume is made on two transistors having the type of transistors of the input differential cascade and an additional resistor connected in parallel with the base-emitter junction of one current source transistor, between the collector and base of which the base-emitter junction of the other current transistor is connected, whose collector is the output, the current source, and the base, the input for connecting the bias voltage source, while the current supply element is made on an additional transistor connected in accordance with the scheme Itter and IME ltsim type current source transistor, the base of the additional transistor is connected to the emitters of transistors reflector current collector - to the emitter of emitter follower transistor, the initial bias current proximity with differential stage proportional to the current source via a further resistor electricity- input differential stage. ig.2 Compiled by I. Vod Khin Editor S. Patrusheva Tehred M. Khodanich Proofreader I. Muska Order 5445/54 Circulation 884 VNIIPI State Committee for Inventions and Discoveries at the State Committee on Science and Technology of the USSR 113035, Moscow, Zh-35, Rauschska nab., A / 5 Fi.Z Subscription