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Problem 5: Consider the CG amplifier

shown in Figure 5. It takes a current source

input (Ip with source resistance, Rp = 5092)

and produces a voltage output, Vout. Assume

that IB = 2.5mA1.25mA, VDD = 1.8V, μnCox 1

140μA/V², μpCox = 60μA/V², VTn

and |VTp = 0.5V, n = 0.1V-¹, and p

0.1V¹, unless otherwise specified.

=

0.4V,

=

Vout 1

31

VDD.

MI

RG

10 WB

L

Figure 5

(a) Design the amplifier such that Rin RP,

and "transimpedance" gain, Vout/Ip-10092. In

other words, determine the (W/L) of

transistor M₁, and resistor Rp. For the sake of

simplicity, assume that gmro>>1.

(b) Suggest a modified design to increase the

"transimpedance" gain, Vout/IP, as much as possible, while still maintaining Rin = Rp. You

are free to make any modifications but make sure that (1) ID = IB = 2.5mA1.25mA and (ii)

the overdrive, VGS - VTH, of all transistors is > 125mV62.5mV. Identify all component

values for your modified design and calculate it's Rin and Vout/IP. Note: 60% of this part's

score is in showing at least 1.5x improvement over part (a). The rest is graded depending

on how much improvement you achieve.

(10 + 15 = 25 points)

IB/10

W₂