Hello,
i want to specify the charakteristics of an amplifier!
Therefore ai have writen a script in hspice which is specifying the Iput Offset Voltage Vos and the Input Bias Current Ios. I know, that for specifiyng the Vos, ihave to put two exactly same Voltage sources (as it is shown bellow) on the invering and non-inverting inputs of the amplifier and measure the output Voltage.
****Voltage Sources****** VDD VDD 0 0 VSS VSS 0 0
*************************
****Stimuli*********************************************************** VinnDut_Vos 0 innDut_Vos dc .1 *sin(0, 0.1, 5Hz,0,0,0) VinpDut_Vos 0 inpDut_Vos dc .1 *sin(0, 0.1, 5Hz,0,0,0) vbiasDut_Vos vbiasDut_Vos 0 5
**********************************************************************
What shall i have to do when measure the input bias current? Shall i do it in the same way?
I have distinguished two cases: a) very low Input bias curernt b) normal low input bias current?
For the first case i have writen for the operatin circuit this script:
**** Input Bias Offset (Ios) specification
**** Ios=I_B(+)-IB(-)
**** I_B=C*(\\delta(out)/(\\delta(t))
**** a) Extremly low Ios*****
VinnDut_Ios_low 0 innDut_Ios_low dc 1 *sin(0, 0.1, 5Hz,0,0,0) VinpDut_Ios_low 0 inpDut_Ios_low dc 1 *sin(0, 0.1, 5Hz,0,0,0) VbiasDut_Ios_low vbiasDut_Ios_low 0 5
*Circuit for measuring extremely low Ios*
*Rsp 0 inpDut_Ios_low 1 *short out Capacitor C1 to test I_B(-) Rsm innDut_Ios_low outDut_Ios_low 1 *short out Capacitor C2 to test I_B(+) C2 innDut_Ios_low outDut_Ios_low 1u C1 0 inpDut_Ios_low 1u
and for the second case this one:
**** b)Normal Ios *****
*Input Sources*
VinnDut_IosNorm 0 innDut_Ios_Norm dc .1
*sin(0, 0.1, 5Hz,0,0,0) VinpDut_IosNorm 0 inpDut_Ios_Norm dc .1
*sin(0, 0.1, 5Hz,0,0,0) vbiasDut_IosNorm vbiasDut_Ios_Norm 0 5 vbiasGen_IosNorm vbiasGen_Ios_Norm 0 5
*Device Under Test(DUT)*
XDutIosNorm VDD VSS vbiasDut_Ios_Norm inpDut_Ios_Norm innDut_Ios_Norm outDut_Ios_Norm DA
*General OpAmp Type*
XGenIosNorm VDD VSS vbiasGen_IosNorm 0 innGen_Ios_Norm outGen_Ios_Norm DA
*Circuit for measuring normal Ios*
RoutDut_Ios_Norm outDut_Ios_Norm innGen_Ios_Norm 10k Rm 0 1 100 Rp 0 3 100 Rbn 1 innDut_Ios_Norm 1 *Rbn short out to test IB(+) Rbp 3 inpDut_Ios_Norm 1000K *Rbp short out to test IB(-) R2 3 outGen_Ios_Norm 100 CinGen innGen_Ios_Norm outGen_Ios_Norm 1u
Can anyone tell me if i have to put the same input voltages, in the same way with i did for the Vos specification? Or shall i have to test the Vos without input Voltages?
Regards
Ioannis
P.S. Do anyone know a hspice forum?