OpAmp (Operational Amplifier)
Symbol
Available in ADS
Parameters
Name 
Description 
Units 
Default 

Gain 
Open loop DC gain of amplifier 
dB 
100 
CMR 
Common mode rejection ratio 
dB 
None 
Rout 
Output resistance 
Ohm 
100 
RDiff 
Differential input resistance 
MOhm 
1 
CDiff 
Differential input capacitance 
F 
0 
RCom 
Common mode input resistance 
MOhm 
1 
CCom 
Common mode input capacitance 
F 
0 
SlewRate 
Signal slew rate 
V/sec 
1e+6 
IOS 
Input offset current 
A 
0 
VOS 
Input offset voltage 
V 
0 
BW 
Gain bandwidth product (unity gain bandwidth) 
MHz 
1 
Pole1 
Dominant pole frequency (overides BW parameter) 


Pole2 
Additional higher order pole frequency 


Pole3 
Additional higher order pole frequency 


Pole4 
Additional higher order pole frequency 


Pole5 
Additional higher order pole frequency 


Zero1 
Feed forward zero frequency 


Inoise 
Input spectral noise current 
A/sqrt(Hz) 
0 
Vnoise 
Input spectral noise voltage 
V/sqrt(Hz) 
0 
VEE 
Negative supply voltage 
V 
15 
VCC 
Positive supply voltage 
V 
15 
DeltaVEE 
Delta difference between saturated voltage and negative supply voltage (see note 4) 
V 
0.3 
DeltaVCC 
Delta difference between saturated voltage and positive supply voltage (see note 4) 
V 
0.3 
Range of Usage
RDiff > 0
CDiff > 0
RCom > 0
CCom > 0
by default:
CMR = ∞
Pole2 = ∞
Pole3 = ∞
Pole4 = ∞
Pole5 = ∞
Zero1 = ∞
Notes/Equations
 The BW parameter is the GainBandwidth product, i.e. it is the frequency at which the gain is unity or 0 dB. Pole1 is the basic amplifier pole and corresponds to the frequency where the gain starts sloping downward.
BW and Pole1 can be specified simultaneously; however, if both are entered, Pole1 will override BW, and Pole1 must then be entered as BW/Gain. The Gain parameter is the open loop gain of the opamp and it must be converted out of dB only for use in setting Pole1, i.e., Gain=10^{Gain_dB/20}.  To match the phase shift from the data sheet, adjust the values of Pole2 through Pole5.
 Zero1 is used for operational amplifiers with feedforward or leadlag compensation networks.
 Output voltage is generally less than the rail voltage (VCC and VEE). Use DeltaVCC and DeltaVEE to specify the difference between the rail voltage and actual output voltage. For example, if VCC is +5V and the positive output is +4.5V, set DeltaVCC to 0.5V.
 This opamp is a nonlinear model. If your circuit cannot achieve convergence using this model, use the OpAmpIdeal linear model.
 The relationship between input and output voltages is given in the equation:
Im × tanh(Vin/Im)=Vout/A0  10 × (VclipVout) + d/dt (Vout × Tau1/A0)
where
A0 is open loop DC gain
Vclip = Vout as long as it is not limiting
Im = SlewRate × Tau1/A0
Tau1=A0/2/π/BW when Pole1=0, otherwise Tau1=1/2/π/BW  In releases before ADS 2008, the OpAmp component contributed noise from the following noise contributors: AMP1.SRC1 and AMP1.SRC2. Starting with ADS 2008, only one noise contributor, called AMP1, is published.