Each manufacturer uses a specific code & assigns a specific type of number to the ICs produced.

The following are the codes for different manufactures of ICs:

•  IC741 – op. amp
• Fairchild – uA, uA7
• National Semiconductors – LM, LH, LF, TBA
• Motorola – MC, MFC
• RCA – CA, CD
• Texas Instruments – SN
• Signetics – N/S, NE/SE
• Burr_Brown – BB

## Ideal and Practical op-amp's :

### Ideal Operational Amplifiers :

#### Inverting amplifier :

this amplifier has non-inverting terminal ground and input is applied to the inverting terminal through a resistive network. The figure shows the circuit of an inverting amplifier:

As, V_d= 0, node ‘a’ is at ground potential for an ideal op-amp

therefore, i_1, through R_1 is i_1= V_1/R_1
Op-amp draws no current and V_o= -i_1*R_f= -V_i* R_f/R_1

therefore, gain of amp closed loop gain (A_(cl) = V_0/V_i = -v_i R_f/R_i
A_ci = -R_f/R_i

Alternatively, node equation at ‘a’ is
( V_a – V_i)/R_1 + (V_a – V_0)/R_F = 0
V_a = 0  (virtual ground)

therefore, -V_i/R_f – V_0/ R_f = 0

A_cc = V_0/V_1 = -R_f/R_1

#### Non – inverting Amp :

If a signal is applied to the non – inverting input terminal allow with the feedback resistor and inverting amplifier.
The figure shows the circuit of non – inverting amplifier: