## Lecture 16 :- Frequency Response of Amplifier

Common Data : VDD = 1.8V , Lmin  = 0.18µm, µ0N = 350cm2/V s, µ0P  = 100cm2/V s, |VTH | = 0.55, tox = 3.8nm, λ = 0.07V−1, χ = 0.1.

1. Use the Miller approximation to calculate the frequency of the small signal voltage gain of a common source stage as shown in Fig. 21, using  and the following transistor data. Ignore channel-length modulation.  Figure 21: Figure for Question 1

2. Calculate the frequency of the circuit in Fig. 22 assuming the following parameter values. Figure 22 : Figure for Question 2  Assume 3. Use zero value time constant method to estimate the small signal dominant pole for the current gain of the cascode current mirror shown in Fig. 23. Assume an input ac current source in parallel with and a zero load impedance with The bias current Compare your answer with the value of the devices. Device parameters are Ignore channel length modulation and substrate effect. Given  Figure 23 : Figure for Question 3

4. The ac schematics of a common source stage and a common source common gate(cascode) stage are shown below, with and Using the transistor and oper- ating point data as Given  Assume 1. Calculate the low frequency small signal voltage fain for each circuit
2. Use the zero value time constant method to calculate and compare the frequencies of teh gains of the two circuits .
3. Estimate the 10% to 90% rise times for each circuit for a small step input and sketch the output voltage waeform over 0 to 300ms for a step input Figure 24 : Figure for Question 4

5. Find an expression for the transfer function of an source follower amplifier (Fig.25). Ignore body effect. Figure 25 : Figure for Question 5