Question

| 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)

Fig: 1