The BJT is define with these parameters: D10.2 In this design problem we have a

Question

The BJT is define with these parameters:

D10.2 In this design problem we have a common-emitter current amplifier driving a second current amplifier across the chip with an input resistance of 5 k2. The line which connects these two amplifiers has 2 pF capacitance to ground. The circuit is shown in Fig. D10.2. Assume ro (a) Choose Isur such that the DC current gain oi,-50. (b) The pole at the output of the amplifier is due to the parasitic line capac- tance and the output resistance of the amplifier in parallel with the 5 k load resistance.What is the frequency of this pole in rad/s? +2.5 V SUP OUT BIAS -2.5 V Figure D10.2

Explanation / Answer

a) isup + iout= B(beta)* (ibias + is)

ibias is small so it can be neglected so isup=100*is-iout = 100*10-17- (is*-50)

isup= 150*10-17 A

b) f = 1/2*pi*B*R*C*

f= 1/2*pi*100*5k*2*10-12

= 0.16 MHz

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