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VGA

Variable gain amplifier

Library

Elements

Description

The VGA block models a RF Blockset™ variable gain amplifier. The Simulink® signal controls the non-linear gain. The VGA output voltage is a function of the input voltage:

Vout=g*Vin+c2*Vin2+c3*Vin2

The table shows the formulas for the coefficients, g, c2, and c3

Coefficient Formulae

 Input ReferredOutput Referred
g

g=2G*Zout*Zin|Zin|

c2

C2=g2*IP2*Zinvolts1

C2=g28*IP2*Zoutvolts1

c3

C3=43.g2*IP3*Zinvolts2

C2=43.g38*IP3*Zoutvolts2

The three Simulink input ports are Gain, IP2 (second-order intercept point), and IP3 (third-order intercept point). In is the RF Blockset voltage input and OUT is RF Blockset voltage output.

Parameters

Input impedance (Ohm)

Input impedance of the amplifier, specified as a scalar. The default value is 50  ohms.

Output impedance (Ohm)

Output impedance of the amplifier, specified as a scalar. The default value is 50  ohms.

Intercept points convention

Input-referred or output-referred convention for IP2 or IP3 intercept points, specified as Input or Output.

The default is Output.

Ground and hide negative terminals

Select this option to internally ground and hide the negative terminals. Clear the option to expose the negative terminals. By exposing these terminals, you can connect them to other parts of your model.

By default, this option is selected.

See Also

Introduced in R2015b

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