1

Figure 7.12 The basic BJT differential-pair configuration.

2

Figure 7.13 Different modes of operation of the BJT differential pair: (a) The differential pair with a common-mode input signal vCM.

3

Figure 7.13 Different modes of operation of the BJT differential pair: The differential pair with a “large” differential input signal.

4

Figure 7.13 The differential pair with a large differential input signal of polarity opposite to that in (b).

5

Figure 7.13 The differential pair with a small differential input signal vi. Note that we have assumed the bias current source I to be ideal (i.e., it has an infinite output resistance) and

thus I remains constant with the change in vCM.

6

Figure 7.14 Transfer characteristics of the BJT differential pair of Fig. 7.12 assuming a = 1.

Figure 7.6 Normalized plots of the currents in a MOSFET differential pair.

Note that VOV is the overdrive voltage at which Q1 and Q2 operate when conducting drain currents equal to I/2.

8

Figure 7.15 The transfer characteristics of the BJT differential pair

The linear range of operation can be extended

by including resistances in the emitters.

Exercise 7.8

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Figure 7.16 The currents and voltages in the differential amplifier when a small differential input signal vid is applied.

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Figure 7.17 A simple technique for determining the signal currents in a differential amplifier excited by a differential voltage signal vid; dc quantities are not shown.

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Figure 7.18 A differential amplifier with emitter resistances. Only signal quantities are shown (in color).

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Figure 7.19 Equivalence of the BJT differential amplifier :

Two common-emitter amplifiers

14

Figure 7.20 The differential amplifier fed in a single-ended fashion.

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Figure 7.19 Equivalence of the BJT differential amplifier :

Two common-emitter amplifiers

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Figure 7.4 The MOS differential pair with a differential input signal vid applied.

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Figure 7.20 The differential amplifier fed in a single-ended fashion.

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Figure 7.21 The differential half-circuit and its equivalent circuit model

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Figure 7.22 The differential amplifier fed by a common-mode voltage signal vicm.

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Figure 7.23 (a) Definition of the input common-mode resistance Ricm. (b) The equivalent common-mode half-circuit.

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Figure 7.24 Circuit for Example 7.1.