Band-Limited Op-Amp
R2026bModel band-limited operational amplifier
Band-Limited Op-Amp block
To add a block to a model, double-click the canvas and start typing the block name. Then, select the block from the list.
Libraries:
Simscape /
Electrical /
Integrated Circuits
Description
The Band-Limited Op-Amp block models a band-limited operational amplifier. If the voltages at the positive and negative ports are Vp and Vm, respectively, the output voltage is:
where:
A is the gain.
Rout is the output resistance.
Iout is the output current.
s is the Laplace operator.
f is the 3-dB bandwidth.
The input current is:
where Rin is the input resistance.
The block does not use the initial condition you specify using the Initial output voltage, V0 parameter if you select the Start simulation from steady state check box in the Simscape™ Solver Configuration block.
Examples
Model Operational Amplifier with Noise
Incorporate noise into an electrical simulation. The circuit models an amplifier with a high-frequency roll off frequency of 10MHz. The Band-Limited Op-Amp block adds the noise. The Voltage Source block, Vn, specifies an equivalent voltage noise density of 20 nV/Hz^0.5. You can also add the thermal noise from the resistors R1 and R2 by setting the Noise mode parameter of the two Resistor blocks to Enabled. However, running this model with different combinations of noise sources shows that the main source of noise is the equivalent noise voltage.
Linear Voltage Regulator with Feedback
A simple voltage regulator circuit constructed from discrete components. A fluctuating supply is modeled as 20V DC plus a 1V sinusoidal variation. The zener diode D1 sets the non-inverting input of the op-amp to 3.2V, and hence as the op-amp has a large gain, the op-amp inverting input and output are also at 3.2V. Hence the regulator voltage output is regulated to be 3.2*(1000+470)/470=10V. The NPN bipolar transistor is required to provide higher currents than is possible from a typical op-amp. The model can be used to check circuit operation, and to support selection of components to achieve the desired voltage regulation.
Model Triangle Wave Generator Using Operational Amplifiers
Model a triangle wave generator circuit by using two Band-Limited Op-Amp blocks. The first stage of the circuit represents a comparator constructed from an op-amp. Two Diode blocks model the Zener diodes that limit the output of the comparator to plus or minus 5 V. These limits result in a square wave.
Design Anti-Aliasing Filter for Analog-to-Digital Converters
Design an analog anti-aliasing filter that you can use with an analog-to-digital converter (ADC). In this example, the filter cut-off frequency is 500 Hz and the sampling frequency is 1000 Hz.
Ports
Conserving
Parameters
Programmatic Use: Add Block
To add the block programmatically, use the add_block function with one of these library block paths as the source.
"ee_lib/Integrated Circuits/Band-Limited Op-Amp"
Example: add_block("ee_lib/Integrated Circuits/Band-Limited Op-Amp","myModel/myBlock",MakeNameUnique="on")
Extended Capabilities
Version History
Introduced in R2008a
