Parameters of OP-AMP M.S.P.V.L Polytechnic College, Pavoorchatram.

Circuit Symbols of OP-AMP

Parameters of OP-AMP  Input offset voltage  Input offset current  Input BIAS current  Large signal voltage gain  Output voltage swing  Differential input resistance Ri  Input capacitance Ci  Common mode rejection ratio  Supply voltage rejection ratio  Slew rate  Gain bandwidth product

Input offset voltage  Input offset voltage is 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.

Input offset voltage

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).

Input offset current

Input BIAS current  I B is the average current flows in the Inverting and Non-Inverting terminal of OP-AMP. IB = (IB1 + IB2 )/2  Typical value for 741 is 500mA

Input BIAS current

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.

Large Signal voltage Gain

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.

Output Voltage Swing

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.

Differential Input Resistance Ri

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.

Input Capacitance Ci

Common Mode Rejection Ratio  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

Common Mode Rejection Ratio

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

Supply Voltage Rejection Ratio

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

Slew Rate

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.

Gain Bandwidth Product

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