Preamplifi ers and Input Signals 207having various drive current/output current ratios, for incorporation into discrete
component circuit designs.
The simple amplifi er circuit of Figure 7.32 can be elaborated, as shown in Figure 7.39 ,
to employ these additional circuit refi nements, which would have the effect of increasing
the open-loop gain, that is, that before negative feedback is applied, by 10 100 and
improving the harmonic and other distortions, and the effective bandwidth by perhaps
3 1 0. From the point of view of the IC designer, there is also the advantage of a
potential reduction in the total resistor count.
These techniques for improving the performance of semiconductor amplifi er stages
fi nd particular application in the case of circuit layouts employing junction FETs and
BC212
Q 5Q 6Q 4 Q 8Q 3R 5
R 4R 6
R 47 R
3
470 REoutGain 10015 V15 VC 110 μF Q
9Q 7
Q 1Q 2R 1Ein100 KR 2
22 K0VBC182BC182BC182 BC182BC212
BC2120V1K100 KBC212BC182- External feadback network
Figure 7.39 : Use of circuit elaboration to improve the two-stage amplifi er of Figure 7.32.