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:


Inverting Circuit

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:
Non - inverting amplifier

Leave a Reply