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Amplifier Circuit With Large Output Signal Swing

IP.com Disclosure Number: IPCOM000077859D
Original Publication Date: 1972-Oct-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Liu, CC: AUTHOR [+2]

Abstract

A circuit is described which overcomes the restricts signal swing capability of transistors which have low BVEV specification.

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Amplifier Circuit With Large Output Signal Swing

A circuit is described which overcomes the restricts signal swing capability of transistors which have low BVEV specification.

BVCEO is the breakdown voltage between collector and emitter electrodes and is defined with base electrode open. Due to the low-voltage breakdown specification, the collector signal swing capability is r restricted, and thereby the usefulness of the transistor is limited.

Fig. 1 shows a conventional amplifier using transistors having a BVCEO of 4 volts. T1 is connected in common-emitter configuration and T2 is connected in common-base configuration. T3 is an emitter follower (common-collector) output stage. The DC voltage operating points are properly chosen as indicated, i.e., VB1 = OV, VB2 = 2.4V, VC2 = 4.2V, VE3 = 3.4V, and a single supply of +6V. The maximum output voltage swing is limited to +/-1.4V or 2.8V, P-P, because the collector of T3 is tied to +6V and negative swing of the output is restricted to +2V to be within the BVCEO of 4 volts.

Fig. 2 shows the improved circuit using the same transistor. The collector load of T2 is divided into three resistors (Ra, Rb and Rc) which supply the proper base biased voltages for T3, T4 and T5. The base of T2 is biased by the resistor divider (R, R') in the emitter circuit of T4. In this arrangement, the collector signal swing of T2, Delta V, is reflected through the resistor-transistor combinations to the base of T4 and T5, and through T4 and...