BRIDGE_I_BIAS1.CIR - CURRENT DRIVEN BRIDGE * * SENSOR BRIDGE RS1 4 11 1 R1 11 12 1K XR2 12 14 20 0 VCR R3 11 13 1K R4 13 14 1K RS4 14 2 1 * * MEASUREMENT WIRES AND RIN OF AMP RS2 12 15 1 RAMP 15 16 100MEG RS3 13 16 1 * * OPAMP CURRENT SERVO VREF 3 0 DC 1V RSENSE 2 0 100 XOP1 3 2 4 OPAMP1 * * * VOLTAGE CONTROL FOR VCR - INCREASING RESISTANCE CHANGE VC1 20 0 PWL(0MS 0.9 10MS 1.1) RD1 20 0 1G * * * SUBCIRCUIT FOR VOLTAGE CONTROLLED RESISTOR (VCR) * RESISTOR - 1,2 CONTROL - 4,5 .SUBCKT VCR 1 2 4 5 ERES 1 3 VALUE = { I(VSENSE)*1K*V(4,5) } VSENSE 3 2 DC 0 .ENDS * * SINGLE-POLE OPERATIONAL AMPLIFIER MACRO-MODEL * connections: non-inverting input * | inverting input * | | output * | | | .SUBCKT OPAMP1 1 2 6 * INPUT IMPEDANCE RIN 1 2 10MEG * DC GAIN (100K) AND POLE 1 (100HZ) EP1 3 0 1 2 100000 RP1 3 4 1K CP1 4 0 1.5915UF * OUTPUT BUFFER AND RESISTANCE EOUT 5 0 4 0 1 ROUT 5 6 10 .ENDS * * * ANALYSIS .TRAN 0.1MS 10MS * * VIEW RESULTS .PLOT TRAN V(15,16) .PROBE .END