Operational Amplifiers I

Purpose
  Sometimes, output of the circuit which we have designed is not optimal for directional application to what we have expected if there is an unwanted offset, or noise. So, we can use an Op, LM741, to eliminate the problem.


Op AMP 741

Figure 1. Circuit Symbol

Figure 2. S.O. Package

Designed Circuit

Figure 3. Designed Circuit

Assumption
  We determine a circuit that includes an inverting amplifier with a gain of -10.It must draw no more than 1mA of current from the sensor, and power supplies should supply no more than 30mW each; moreover, the circuit should be designed with standard 1/4 W resistors. 

Figure 4. Build-up Circuit on Breadboard

Figure 5. The Circuit connected to Multimeter

Calculations
  We calculated for safe values for the resistor, built the circuit, and measured the V_{IN and} 

V_{OUT for the gain.}

• Given

  • V_{1 =} 12.13V

  • V_{2 =  12.06V}                                                                           

   _Result
  

  • Ri = 1K Ω 

  • Rf = 10KΩ 

  • Rx = 1152 Ω 

  • Ry= 104.7 Ω 

  
  

  
  

  Vin (V)	Vout (V)	GAIN	VRi (V)	IRi (uA)	VRf (V)
  0	-0.05	0	0.007	7.00	0.06
  0.25	-2.54	-10.16	0.269	269	2.57
  0.50	-5.08	-10.17	0.536	536	5.12
  0.75	-7.56	-10.08	0.797	797	7.62
  1.00	-9.91	-9.91	0.946	946	9.91

  The power supply current

  Iv1=2.32mA

  Iv2=1.49mA

  
  

  So, Pv1= 12.13*2.32m=28.14mw; Pv2= 12.06*1.49m=17.97mw which satisfy the power supply constraint to supply no more than 30mW each.