Parameters of OPAMP:

16. Gain Bandwidth Product:

The gain bandwidth product is the bandwidth of the OPAMP when the open loop voltage gain is reduced to 1. From open loop gain vs frequency graph At 1 MHz shown in. fig. 6, It can be found 1 MHz for the 741C OPAMP frequency the gain reduces to 1. The mid band voltage gain is 100, 000 and cut off frequency is 10Hz.

Fig. 6

17. Slew Rate:

Slew rate is defined as the maximum rate of change of output voltage per unit of time under large signal conditions and is expressed in volts / m secs.

To understand this, consider a charging current of a capacitor shown in fig. 7.

Fig. 6

If 'i' is more, capacitor charges quickly. If 'i' is limited to I_max, then rate of change is also limited.

Slew rate indicates how rapidly the output of an OPAMP can change in response to changes in the input frequency with input amplitude constant. The slew rate changes with change in voltage gain and is normally specified at unity gain.

If the slope requirement is greater than the slew rate, then distortion occurs. For the 741C the slew rate is low 0.5 V / m S. which limits its use in higher frequency applications.

18. Input Offset Voltage and Current Drift:

It is also called average temperature coefficient of input offset voltage or input offset current. The input offset voltage drift is the ratio of the change in input offset voltage to change in temperature and expressed in m V /° C. Input offset voltage drift = ( D V_io / D T).

Similarly, input offset current drift is the ratio of the change in input offset current to the change in temperature. Input offset current drift = ( D I_io / D T).

For 741C,

D V_io / D T = 0.5 m V / C.
D I_io/ D T = 12 pA / C.