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Problem 3: Consider the amplifier schematic shown

in Figure 3. This is called a folded cascode

amplifier. The transistors are biased such that 21B

splits equally between the two transistors. Please use

the following parameters wherever necessary for

your calculations: IB=2mAlmA, VDD = 1.8V, μnCox

140μA/V², μpCox 60μA/V², V™n = 0.4V, and

|VTp = 0.5V, n = 0.1V-¹, and p = 0.2V¹0.1V-¹,

unless otherwise specified. Ignore channel length

modulation except for parts (d), (e), and (f).

(a) Determine the range of values of R3 for which

M₂ is in saturation.

Vin

R₁≤

"에

M₁

VDD

21B

R;

Yout

M₂ -VDD

Figure 3

(b) Determine (W/L)2-, assuming overdrive is 0.5V.

(c) Assume that (W/L): 40 and dDetermine the range of values of the ratio R₂/R₁ that

keeps M₁ ON, and in saturation. Assuming that (W/L)₁ = 40, determine the ratio

R₂/R1.

(d) Calculate the gm and ro for both transistors.

For the rest, assume that R3 = 200 Ohms and that the capacitors are shorted for ac signals

(e) Calculate the gain (numerical value) of this amplifier.

(f) Calculate the output impedance (numerical value).

(5+5+5+8+4+3 = 30 points)