Self on Audio by Douglas Self

Author:Douglas Self [Self, Douglas]
Language: eng
Format: epub, mobi
ISBN: 9781317520955
Publisher: Taylor and Francis
Published: 2015-10-05T04:00:00+00:00

Vive la differential

The primary motivation for using a differential pair as the input stage of an amplifier is usually its low DC offset. Apart from its inherently lower offset due to the cancellation of the Vbe voltages, it has the added advantage that its standing current does not have to flow through the feedback network. However a second powerful reason is that its linearity is far superior to single-transistor input stages. Figure 23.1 shows three versions, in increasing order of sophistication. The resistor-tail version in Figure 23.1(a) has poor CMRR and PSRR and is generally a false economy; it will not be further considered. The mirrored version in Figure 23.1(c) has the best balance, as well as twice the transconductance of that in Figure 23.1(b).

Figure 23.1 Three versions of an input pair: (a) Simple tail resistor; (b) Tail currentsource; (c) With collector current-mirror to give inherently good lc balance.

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.