Question 22.8: Simulate the operation of the diff-amp in Fig. 22.22 using t......

CMOS Circuit Design, Layout, and Simulation [1366182]

Simulate the operation of the diff-amp in Fig. 22.22 using the parameters from Table 9.1.

Table 9.1 Typical parameters for analog design using the long-channel CMOS process discussed in this book. Note that the parameters may change with temperature or drain-to-source voltage (e.g., Fig. 9.24).

Long-channel MOSFET parameters for general analog design
VDD = 5 V and a scale factor of 1 μm (scale = 1e-6)

Parameter	NMOS	PMOS	Comments
Bias current, $I_D$	20 $\mu A$	20 $\mu A$	Approximate
W/L	10/2	30/2	Selected based on $I_D\ \text{and}\ V_{DS,sat}$
$V_{DS,sat}\ \text{and}\ V_{SD,sat}$	250 mV	250 mV	For sizes listed
$V_{GS}\ \text{and}\ V_{SG}$	1.05 V	1.15 V	No body effect
$V_{THN}\ \text{and}\ V_{THP}$	800 mV	900 mV	Typical
$\partial V_{THN,P}/\partial T$	$-1\ \text{mV/C°}$	$-1.4\ \text{mV/C°}$	Change with temperature
$KP_n\ \text{and}\ KP_p$	$120\ \mu A/V^2$	$40\ \mu A/V^2$	$t_{ox}=200\ \mathring{A}$
$C_{o x}^{\prime}=\varepsilon _{o x}/t_{o x}$	$1.75fF/\mu m^2$	$1.75fF/\mu m^2$	$C_{ox}=C_{o x}^{\prime}WL\cdot (scale)^2$
$C_{oxn}\ \text{and}\ C_{oxp}$	$35fF$	$105fF$	PMOS is three times wider
$C_{gsn}\ \text{and}\ C_{sgp}$	$23.3fF$	$70fF$	$C_{gs}=\frac{2}{3}C_{ox}$
$C_{gdn}\ \text{and}\ C_{dgp}$	$2fF$	$6fF$	$C_{gd}=CGDO\cdot W\cdot scale$
$g_{mn}\ \text{and}\ g_{mp}$	$150\ \mu A/V$	$150\ \mu A/V$	$At\ I_D=20\ \mu A$
$r_{on}\ \text{and}\ r_{op}$	$5\ M\Omega$	$4\ M\Omega$	Approximate at $I_D=20\ \mu A$
$g_{mn}r_{on}\ \text{and}\ g_{mp}r_{op}$	750 V/V	600 V/V	Open circuit gain
$\lambda _n\ \text{and}\ \lambda _p$	$0.01\ V^{-1}$	$0.0125\ V^{-1}$	At L = 2
$f_{Tn}\ \text{and}\ f_{Tp}$	900 MHz	300 MHz	$\text{For}\ L=2,f_T\ \text{goes up if}\ L=2$

Step-by-Step

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The simulation results are seen in Fig. 22.23. Note that when both inputs are at 3.5 V, the output currents are equal. This figure should be to Fig. 22.3.

Note how in Fig. 22.3, the output currents flatten out above a maximum input voltage. Here the current continues to increase.