Operational Amplifier

Model operational amplifier with two or more poles

Since R2021b

• 

Libraries:
Mixed-Signal Blockset / Utilities

Description

Use the Operational Amplifier block to model an operational amplifier with two or more poles. You can create a double-pole amplifier from the important circuit parameters or a multiple-pole amplifier from a transfer function. Use the block to characterize the performance of an operational amplifier as part of a larger circuit system.

Ports

Input

InP — Positive input terminal

scalar

Positive input terminal of the operational amplifier.

Data Types: single | double

InN — Negative input terminal

scalar

Negative input terminal of the operational amplifier.

Data Types: single | double

Output

OutP — Positive output terminal

scalar

Positive output terminal of the operational amplifier.

Data Types: single | double

OutN — Negative output terminal

scalar

Negative output terminal of the operational amplifier.

Data Types: single | double

Parameters

Operational Amplifier Circuit — Type of operational amplifier circuit

Double-pole Circuit (default) | Multipole Circuit

Type of the operational amplifier circuit.

• Double-pole Circuit — Use circuit parameters such as open-loop gain, unity gain bandwidth, maximum tail current, and slew rate to define a simple double-pole circuit.

• Multipole Circuit — Use transfer function poles and zeros to define a multiple-pole circuit.

Programmatic Use

Block parameter: OpampType

Type: character vector

Values: Double-pole Circuit| Multipole Circuit

Default: Double-pole Circuit

Inherit sample interval from input — Inherit sample interval from input

off (default) | on

Inherit the sample interval value from the input. By default, this option is deselected.

Sample interval (s) — Sample interval value used in MATLAB analyses

1e-8 (default) | scalar

Sample interval value the block uses in MATLAB^® analyses, specified as a scalar in seconds.

Dependencies

To enable this parameter, deselect the Inherit sample interval from input option.

Programmatic Use

Block parameter: SampleInterval

Type: character vector

Values: scalar

Default: 1e-8

Simulate using — Select simulation mode

Code generation (default) | Interpreted execution

Select the simulation mode. This option you choose affects simulation performance.

Simulating the model using the Code generation method requires additional startup time, but the subsequent simulations run faster. Simulating the model using the Interpreted execution method may reduce the startup time, but the subsequent simulations run slower. For more information, see Interpreted Execution vs. Code Generation.

Programmatic Use

Block parameter: SimulateUsing

Type: character vector

Values: Code generation| Interpreted execution

Default: Code generation

Signal Parameters

Supply rail high (V) — Maximum supply voltage

5 (default) | real scalar

Maximum supply voltage provided to the Operational Amplifier block, specified as a real scalar in volts.

Programmatic Use

Block parameter: VoltageSupplyPlus

Type: character vector

Values: real scalar

Default: 5

Supply rail low (V) — Minimum supply voltage

-5 (default) | real scalar

Minimum supply voltage provided to the Operational Amplifier block, specified as a real scalar in volts.

Programmatic Use

Block parameter: VoltageSupplyMinus

Type: character vector

Values: real scalar

Default: -5

Input offset voltage (V) — Offset voltage at input terminals

0 (default) | scalar

Offset voltage at the input terminals of the operational amplifier, specified as a scalar in volts. The block uses this value to obtain a zero voltage at the output terminals of the operational amplifier.

Programmatic Use

Block parameter: InputOffsetVoltage

Type: character vector

Values: scalar

Default: 0

Advanced Parameters

Open loop gain (V/V) — Operational amplifier gain without feedback

3e3 (default) | positive real scalar

The gain of the operational amplifier without any positive or negative feedback, specified as a unitless positive real scalar.

Dependencies

To enable this parameter, set Operational Amplifier Circuit to Double Pole Circuit.

Programmatic Use

Block parameter: Gain

Type: character vector

Values: positive real scalar

Default: 3e3

Unity gain bandwidth (Hz) — Frequency at which operational amplifier gain equals unity

10e6 (default) | positive real scalar

The frequency at which the open-loop gain of the operational amplifier becomes unity, specified as a positive real scalar in hertz.

Dependencies

To enable this parameter, set Operational Amplifier Circuit to Double Pole Circuit.

Programmatic Use

Block parameter: FrequencyUnityGain

Type: character vector

Values: positive real scalar

Default: 10e6

Maximum tail current (A) — Maximum current passing through tail MOSFET in operational amplifier circuit

100e-6 (default) | positive real scalar

Maximum value of the current passing through the tail MOSFET (metal oxide semiconductor field effect transistor) in the operational amplifier circuit, specified as a positive real scalar in amperes.

Dependencies

To enable this parameter, set Operational Amplifier Circuit to Double Pole Circuit.

Programmatic Use

Block parameter: InputCurrentMax

Type: character vector

Values: positive real scalar

Default: 100e-6

Slew rate (V/s) — Rate of change of operational amplifier output voltage

10e6 (default) | positive real scalar

The rate of the change of the output voltage of the operational amplifier with respect to time, specified as a positive real scalar.

Dependencies

To enable this parameter, set Operational Amplifier Circuit to Double Pole Circuit.

Programmatic Use

Block parameter: SlewRate

Type: character vector

Values: positive real scalar

Default: 10e6

Output resistance (Ohms) — Resistance at output terminals

10e3 (default) | positive real scalar

Resistance at the output terminals of the operational amplifier, specified as a positive real scalar in ohms.

Dependencies

To enable this parameter, set Operational Amplifier Circuit to Double Pole Circuit.

Programmatic Use

Block parameter: OutputResistance

Type: character vector

Values: positive real scalar

Default: 10e3

Output Capacitance (F) — Capacitance at output terminals

50e-12 (default) | positive real scalar

Capacitance at the output terminals of the operational amplifier, specified as a positive real scalar in farads.

Dependencies

To enable this parameter, set Operational Amplifier Circuit to Double Pole Circuit.

Programmatic Use

Block parameter: OutputCapacitance

Type: character vector

Values: positive real scalar

Default: 50e-12

Transfer function poles — Poles in transfer function in Laplace domain

[-2.09e+04 -8.62e+07] (default) | column vector

Poles in the transfer function of the operational amplifier in the Laplace domain, specified as a column vector in rad/s.

If you set Operational Amplifier Circuit to Double-pole Circuit, the block automatically calculates the poles for you from the circuit parameters. If you set Operational Amplifier Circuit to Multipole Circuit, you can specify the poles.

Programmatic Use

Block parameter: Poles

Type: character vector

Values: column vector

Default: [-2.09e+04 -8.62e+07]

Transfer function zeroes — Zeros in transfer function in Laplace domain

[-9.14e+07] (default) | column vector

Zeros in the transfer function of the operational amplifier in the Laplace domain, specified as a column vector in rad/s.

If you set Operational Amplifier Circuit to Double-pole Circuit, the block automatically calculates the zeros for you from the circuit parameters. If you set Operational Amplifier Circuit to Multipole Circuit, you can specify the zeros.

Programmatic Use

Block parameter: Zeros

Type: character vector

Values: column vector

Default: [-9.14e+07]

Analysis

Include Z-domain approximation — Include z-domain approximation while plotting open loop response

off (default) | on

When plotting the open-loop response of the operational amplifier, include the z-domain (discrete time) approximation in addition to s-domain transfer function.

Plot open loop response — Plot open loop response of op-amp

button

Plot the s-domain transfer function of the open loop response of the operational amplifier. The plot also reports the unity gain bandwidth and phase margin. You can choose to include the z-domain approximation.

Version History

Introduced in R2021b

R2024a: Plot Open Loop Response

You can now plot the open loop response of the operational amplifier, along with the z-domain approximation.