Op-amp Parameters

1)Input offset Voltage

Input offset voltage is the the voltage that must be applied between the two input terminals of an op-amp to null the output.Typical value of 741 IC is 6mV dc.

2) Input offset current

The algebraic difference between the current in the inverting and non inverting terminal is known as the input offset current Iio.As the matching between two terminals increases,the difference between IB1 and IB2 become smaller.Typical value for 741 IC is 200mA(max).

3)Input Bias Current

IB is the average current flows in the inverting and non-inverting terminal of an op-amp.

IB = (IB1 + IB2 )/2

Typical value for 741 is 500mA

4) Large Signal Voltage gain

It is the ratio of the output voltage and the differential input voltage

A = Output voltage/Differential input

= Vo/Vid

Typical value for 741 IC is 200,000.

5) Output Voltage Swing

This parameter indicates the values of positive and negative saturation voltage of the op-amp.For 741IC,it is +13 and -13V.

6) Differential input resistance Ri

Differential input resistance Ri is the equivalent resistance that can be measured at either the inverting or non-inverting input terminals with the other terminal connected to ground.Typical value for 741 IC is 2 mega ohm.

7) Input Capacitance Ci

Input capacitance is the equivalent capacitance that can be measured at either the inverting or non-inverting input terminal with the other terminal connected to ground.Typical value for a 741 IC is 1.4 pF.

8) Common Mode Rejection Ratio(CMRR)

When the same voltage is applied to both the input terminals the voltage is called a common mode voltage Vcm and the op-amp is said to be operating in the common mode configuration,CMRR is defined as the ratio of the differential voltage gain to common mode gain.

CMRR = Ad/Acm

9) Supply voltage Rejection Ratio

The change in an op-amps input offset voltage Vio caused by variations in the supply voltage is called the SVRR.It is expressed in microvolts per volt or in decibels.

SR= ΔVio/ΔV

Typical value for a 741IC is 150μV/V

10) Slew Rate

Slew rate is defined as the maximum rate of change of output voltage per unit of time and is expressed as volt per micro second.

SR=(|dVo|/|ds|)max ie V\μs

11) Gain Bandwidth Product

The gain bandwidth product(GB) is the bandwidth of the op-amp when the voltage gain is 1.Typical value for 741 IC is 1MHz.

Written by John on October 13th, 2008 with 1 comment.
Read more articles on Linear Integrated Circuits and op-amp.

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