Op amp 741 or Operational Amplifier 741 IC
- Pin 1 is balance pin
- Pin 2 is inverting input
- Pin 3 is non inverting input
- Pin 4 is negative power supply pin
- Pin 5 is balance pin
- Pin 6 is output pin
- Pin 7 is positive power supply pin
- Pin 8 does not have any connection
The circuit symbol of op amp 741 is shown below.
In an op amp symbol, + sign is marked on non-inverting input and - sign is marked on inverting input.
When an signal is applied to the inverting input pin, the output will appear in opposite polarity. When an signal is applied to the non inverting input, the output will appear in same polarity as input. The equivalent circuit of an op amp is drawn below.
The output of an op amp is a voltage controlled voltage source with a resistance R0 in series with it. The input resistance Ri exists between inverting and non-inverting input. Ri is the Thevenin equivalent resistance between input terminals. Similarly, output resistance is the Thevenin equivalent resistance seen at output. The input voltage of an op amp is the difference of the voltages applied at input terminals. This is called differential voltage and it is generally denoted as
Where v2 and v1 are input voltages.
An op amp multiplies this differential voltage with the gain A. This gained differential voltage Avd, then appears at the output terminal. This is known as open loop voltage gain. The typical parameters of a 741 Op-amp is furnished in the table below,
|Parameters||Typical Range||Ideal Value|
|Open Loop Gain(A)||105 to 108||∝|
|Input Resistance(Ri)||105 to 1013||∝|
|Output Resistance(Ro)||10 to 100||0|
If the supply voltage is denoted by Vcc in an op amp then, mathematically we can write, That means, output voltage v0 of an op amp cannot reach below –Vcc and above Vcc. Inside this range v0 is linearly proportional to the input differential voltage vd. This can be graphically represented as, An op amp is intended to be operated in that linear region.