Figure 1. Ammeter circuit
Lab 1 Ammeter Simulation
Evaluate the ammeter shown in Figure 1. The opamp has a gain of 108,
an input impedance of 100 MEG,
an input offset voltage of 1 mV, and an input offset current of 100 pA.
Run SPICE simulations to determine the effect of the nonideal opamp on the ammeter accuracy.
Figure 1. Ammeter circuit
Figure 2 Opamp model
Opamp SPICE Subcircuit
.subckt opamp 1 2 3 * opamp input impedance is 100MEG Rin 1 2 100MEG VOS 1 4 1E-3 IOS 4 2 1e-10 * * A voltage controlled voltage source models the opamp. * V+ in is node 1, V- in is node 2, and Output is node 3 * The gain is 1E8 EOPAMP 5 0 1 2 1E8 ROUT 5 3 100 .ends