Question 8.18: Verify Ex. 8.17 using SPICE. Use a voltage-controlled voltag......

The schematic used for simulations is seen in Fig. 8.37. Instead of connecting the op-amp’s noninverting input (the + input) to ground directly, we connect it to ground via a zero volt DC supply so that, in the simulation, we have an “input.” (Recall comments about how the AC magnitude of this input source affects the input-referred noise.) The SPICE netlist is

Comment line; the first line of a netlist is ignored by SPICE

.noise    V(Vout,0)                Vplus      dec     100    1      1000G

Vplus     Vplus       0                  dc          0        ac     1

Rf           Vout        Vminus      100k

Cf            Vout      Vminus                      1000pf

Eopamp Vout                             0          Vplus   Vminus   100MEG

.print noise all

.end

The SPICE output is

TEMP=27 deg C

inoise_total = 4.142190e-12

onoise_total = 4.142190e-12

For the 1,000 pF capacitor, this gives 2.03 μV. Resimulating with the 1 pF capacitor, gives 64.3 μV.