Get premium membership and access questions with answers, video lessons as well as revision papers.

Explain what Summing Amplifiers are and how it works

      

Explain what Summing Amplifiers are and how it works

  

Answers


Wilfred
- A summing amplifier is an inverted OP-amp that can accept two or more inputs. The output voltage of a summing amplifier is proportional to the negative of the algebraic sum of its input voltages.
Hence the name summing amplifier. Fig. 9.3 shows a three-input summing amplifier but any number of inputs can be used. Three voltages V1, V2 and V3 are applied to the inputs and produce currents I1, I2 and I3. Using the concepts of infinite impedance and virtual ground, you can see that inverting input of the OP- amp is at virtual ground (0V) and there is no current to the input. This means that the three input currents I1, I2 and I3 combine at the summing point A and form the total current (If) which goes through Rf as shown in Fig. 9.3.
slew7a16820191200.png
- When all the three inputs are applied, the output voltage is:
slew816820191200.png
- Thus the output voltage is proportional to the algebraic sum of the input voltages (of course neglecting negative sign). An interesting case results when the gain of the amplifier is unity. In that case, Rf = R1 = R2 = R3 and output voltage is
Vout = – (V1 + V2 + V3)
- Thus, when the gain of summing amplifier is unity, the output voltage is the algebraic sum of the input voltages.

Summing amplifier with gain greater than unity: When Rf is larger than the input resistors, the amplifier has a gain of Rf /R where R is the value of each input resistor. The general expression for the output voltage is;
slew8a16820191200.png
- As you can see, the output voltage is the sum of input voltages multiplied by a constant determined by the ratio Rf /R.
Wilfykil answered the question on August 16, 2019 at 09:44


Next: Below is radioactive decay series starting from Q316820191223.png and ending at Q316820191226.png
Previous: Use tables of square ,cubes roots and reciprocals to find the value of x if

View More Electronics Questions and Answers | Return to Questions Index


Learn High School English on YouTube

Related Questions