Electronic Devices and Amplifier Circuits

Cascaded Tuned AmplifiersA------A c1 2 3 4Figure 9.15. Amplitude characteristics for two tuned stages with different degrees of staggeringFor the curves in Figure 9.15, α is held constant while β is increased in steps. Curve 1 is for synchronoustuning, Curve 2 is for understaggering with φ c = 70° , Curve 3 is for flat staggering, andCurve 4 is for overstaggering with A p ⁄ A c = 1.1 . The half−power bandwidths are indicated by thesolid dots on these curves.For the flat−staggered case β = α, r = 1, and sinφ c = 1 . Thus, from relations (9.71) and (9.72)we obtain1A c = A p = --g 22 m R 1 R 2(9.85)Letting B fsdenote the bandwidth of two stages with flat staggering and BW the 3–dB bandwidthof one of the stages, from (9.84) we obtainThe gain−bandwidth product for the flat−staggered amplifier is given byω cB fs = 2 2BWω(9.86)A c B fs = ( 1 ⁄ 2) ( g 2 m R 1 R 2 )BWFor two synchronously tuned stages we denote the bandwidth of two stages asgain−bandwidth product, using relation (9.60) we obtainA c B syn = A 2 1 BW 1 2 1 ⁄ 2– 1 = 0.64( g 2 m R 1 R 2 )( BW)B syn(9.87). Then, for the(9.88)The foregoing discussion of stagger−tuned amplifiers considers only the case in which the poles arestaggered along a line parallel to the imaginary axis. If the poles do not lie on the same vertical line,skewed frequency characteristics result, and, in accordance with the discussion in Section 9.1, thisfact may cause distortion of the envelopes of AM signals.Electronic Devices and Amplifier Circuits with MATLAB® / Simulink® / SimElectronics® Examples, Third EditionCopyright © Orchard Publications9−25