Figure 7.12 The basic BJT differential-pair configuration. sedr42021_0712.jpg

Figure 7.13 Different modes of operation of the BJT differential pair: (a) The differential pair with a common-mode input signal vCM. sedr42021_0713a.jpg

Figure 7.13 Different modes of operation of the BJT differential pair: The differential pair with a “large” differential input signal. sedr42021_0713a.jpg

Figure 7.13 The differential pair with a large differential input signal of polarity opposite to that in (b). sedr42021_0713c.jpg

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. sedr42021_0713c.jpg

Figure 7.14 Transfer characteristics of the BJT differential pair of Fig. 7.12 assuming a = 1. sedr42021_0714.jpg

Note that VOV is the overdrive voltage at which Q1 and Q2 operate Figure 7.6 Normalized plots of the currents in a MOSFET differential pair. sedr42021_0706.jpg Note that VOV is the overdrive voltage at which Q1 and Q2 operate when conducting drain currents equal to I/2.

Figure 7.15 The transfer characteristics of the BJT differential pair sedr42021_0715a.jpg The linear range of operation can be extended by including resistances in the emitters.

Exercise 7.8

Figure 7.16 The currents and voltages in the differential amplifier when a small differential input signal vid is applied. sedr42021_0716.jpg

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. sedr42021_0717.jpg

Figure 7. 18 A differential amplifier with emitter resistances Figure 7.18 A differential amplifier with emitter resistances. Only signal quantities are shown (in color). sedr42021_0718.jpg

Figure 7.19 Equivalence of the BJT differential amplifier : Two common-emitter amplifiers sedr42021_0719a.jpg

Figure 7.20 The differential amplifier fed in a single-ended fashion. sedr42021_0720.jpg

Quiz # 2 (Syn A) For the BJT Differential Pair shown in the given figure, find the value of the input differential signal vid = vB1 – vB2, that causes iE1 = 0.80I.

Quiz # 2 (Syn B) Using the above two equations, plot the collector currents iC1 and iC2 (normalized to the total bias current I) versus the normalized differential input voltage vid/VT.

Figure 7.19 Equivalence of the BJT differential amplifier : Two common-emitter amplifiers sedr42021_0719a.jpg

Figure 7.4 The MOS differential pair with a differential input signal vid applied. sedr42021_0704.jpg

Figure 7.20 The differential amplifier fed in a single-ended fashion. sedr42021_0720.jpg

Figure 7.21 The differential half-circuit and its equivalent circuit model sedr42021_0721ab.jpg

Figure 7.22 The differential amplifier fed by a common-mode voltage signal vicm. sedr42021_0722a.jpg

Figure 7. 23 (a) Definition of the input common-mode resistance Ricm Figure 7.23 (a) Definition of the input common-mode resistance Ricm. (b) The equivalent common-mode half-circuit. sedr42021_0723a.jpg

Figure 7.24 Circuit for Example 7.1. sedr42021_0724.jpg