Commonly Used Functions for Approximating Constant Gain or Linear Phase

Fig. 9-1 Assumed ideal passband shape In the filter amplifier the usual problem is to approximate an ideal amplitude response, such as that shown in Fig. 9-1, where the gain is constant in some passband region (wi to co2) and zero outside this passband. In practice, with only lumped, linear networks neither the constant gain in the passband nor the infinite rejection of signals outside the passband can be obtained. Therefore our problem is to discover suitable gain func- for a filter amplifier....

Problems

A given two-port network has the following h parameters hn 25 ohms, hn 104, hn -1, ka 10-6 mho. What are the values of the z and y parameters for the network 2-2. Assume that a two-port network characterized by the h parameters is to operate from a source Rg and load Rl- (Assume that the parameters are real.) a. Derive an equation for the insertion power gain. b. Derive an equation for the available power gain. 2-Sa. Show that the impedance looking into the input of a two-port network...

Info

Fig. 4-33 Gaussian amplitude response. the literature that examine the relative importance of the types of distortion we shall shortly consider two of these analyses. Actually, of course, in most simple amplifier interstage networks of the type already presented in this section the amplitude and phase responses are interrelated in a manner characteristic of the broad class of networks identified by the term minimum phase. It will not be possible here to go into the details of the definition of...

War

Fig. 2-8 A model of the junction transistor based upon the theory of the device. r'c The incremental collector resistance. This arises because increasing the collector voltage increases the width of the depletion region surrounding the collector junction. In turn this causes the effective width of the base region to decrease. The change in base width caused by changes in V'c is called base-width modulation. The decreased base width caused by increased V'c reduces the current lost in the base,...

Cgh

Fig. 10-2 Pole cluster about band center for a maximally flat amplifier and the corresponding situation including all poles and zeros. (Narrow band.) given only through the staggered quadruple, although obviously it could be extended as far as desired. Practically, however, the pairs and triples are the most widely used. Higher orders require stages with high Q (poles near the jco axis), sometimes higher than can be obtained in the presence of Table 10-1. Narrow-band Stagger Tuning (Maximally...

Stagger Tuning

The term stagger tuning refers to an amplifier comprising several stages in cascade, in which the stages are not tuned identically to the same frequency but are staggered at frequencies above and below the desired center frequency of the complete amplifier. Not only are the tunings of the individual stages nonidentical, but their bandwidths are also different. The objectives of stagger tuning are twofold 1 a greater gain-bandwidth factor is generally achieved than with a cascade of identical...

Jbn

Fig. 4-38 Response of an amplifier to a pulse input when only amplitude distortion or only phase distortion is present. One analytical study of interest for cases of larger degrees of amplitude or phase distortion than are normally treated with the paired-echoes technique is that of DiToro.1 He treats the case of an amplifier or any other linear network, not necessarily lumped having a steady-state re- 128 Step Response Speed of Rise sponse expressible by the exponential function This is not...

ReqC VieqC LCRRl

The locus of the poles pi, p2 as L varies is shown in Fig. 4-14. The maximum value of L without having complex pi and p2 is that which makes the radical vanish. This value of L gives critical damping. Making L larger introduces oscillatory terms which cause overshoot in the output waveform. Substituting this value of L into Eq. 4-10 gives

S

Two stages tuned to oa2 and oA 2, same 1.088 Note fo is the center frequency of the over-all amplifier, and B is the over-all 3-db bandwidth. 10-3, respectively that the tuning of the low stages is the same, but not that of the high stages. In the narrow-band case the bandwidths of corresponding high and low stages are the same, whereas in the asymptotic case the Q's are the same. Thus the equations of Table 10-3 display the correct geometric symmetry about 0. The differences, though, are quite...

Svo

From Eq. 13-11 2 is seen to have a minimum value at low frequencies of i2 2 qIcB 1 - ao f 0 13-12 1 The fact that the two generators are uncorrelated has the practical effect that the noise power, say at the output of the device, may be computed by calculating the power due to each noise generator separately and summing the two powers to obtain the true total power. The magnitude of i2 as a function of frequency is shown in Fig. 13-5, in which ic2 is seen to start increasing at a frequency...

L

This equation has the same denominator as the equation for the series-peaked circuit however, there is now a zero in Z21 at p Rn L z0. C A 1 M lt r' 1 0hRLZCc R 4r l -aQ Fig. 4-17 A shunt-peaked transistor interstage. Again the value of L may be chosen so that critical damping is obtained this will require the same value of L as before, For this value of L the poles of Z21 are in the same position as for the series-peaked circuit, 2 RL1 r'i R 2 Pi p2 -. 4-30 To compute the rise time for the...