SMDP Instructional Enhancement Programme: 13-24 Nov. 2006

SMDP Instructional Enhancement Programme: 13-24 Nov. 2006

Nagendra Krishnapura (nagendra@iitm.ac.in) 16 Nov. 2006

amplifier model in verilogA

nonlinearity a₁, a₂, a₃

-0.9V +0.9V

2kΩ 2kΩ

1mA W/L W/L

W/L=10(2.5µ/0.18µ) v_outp v_outn

v_out = v_outp-v_outn

v_ip v_in

v_i v_out

v_i = v_ip-v_in

single pole filter (f_3dB)

Figure 1:

1. Model the nonlinearity (upto the third term) and the frequency response (using a single pole re- sponse) of the differential amplifier using ver- ilogA. (Fig. 1)

Simulate the distortion using the verilogA model and compare it to the results from the previous lab session.

Overlay the frequency responses of the transis- tor level circuit and the verilogA model. Where does the model deviate from reality?

2. Model a vco in verilogA and plot its frequency versus control voltage curve forV_ctlfrom -0.5 V

Vctl fvco = fo + KvcoVctl

cos(2πfvcot)

Σ ++ V_ctl

white noise v_n

Figure 2:

to +0.5 V. (Fig. 2)

Add white noise to the control voltage and sim- ulate the output spectral density of the oscilla- tor. Does it match the expected spectral den- sity?

1