Lower comparator monitors the minimum value of the desired range and upper comparator monitors the maximum value of the desired range. To detect the arrival of a particular range of voltage(s) from the swing of an input signal, this circuit is used.Two Op-Amps in comparator mode are used in this circuit. Output equation of Summing Amplifier Simulation of Op-Amp as Summing Amplifier The output of Non-Inverting Summing amplifier follows the equation, The output of inverting amplifier for above mentioned resistor values is, V out=-(V a+V b+V c). If the common node of resistors is connected to V- terminal then it is called Inverting summing amplifier. By varying the R f value, gain of the circuit can be controlled. If R 1=R 2=R 3=R=2*R f then output, V out=V a+V b+V c. The gain of the output can be controlled by selecting appropriate resistance values. Voltages from various sources referred to the common ground are added in this circuit. Output equation of Differential Amplifier Simulation of Op-Amp as Differential Amplifier If V out=V a+V b-V c-V d is the desired output, then connect V c, V d to V- terminal and V a, V b to V+ terminal.Output of the Op-Amp follows the equation, This can be used as an analog Subtractor. The output varies according to the gain of the amplifier circuit between +V sat and -V sat. It is similar to the comparator mode, and in addition the Op-Amp is operated in a closed loop, making it possible to control the voltage gain of the circuit. The difference of the voltage between V+ and V- is amplified in this circuit. Op-Amp as Differential Amplifier/Subtractor Output equation of Inverting Amplifier Simulation of Op-Amp as Inverting Amplifier Output of the Op-Amp follows the equation, So, selection of supply voltage range is important to obtain the desired output voltages. The output varies according to gain of the amplifier circuit between +V sat and -V sat. Inverting amplifier configuration can give unity gain, i.e., V out=-V in. Below is the circuit diagram of inverting amplifier with Dual voltage supply conditions. The polarity of the output voltage is opposite to that of the input. Input is applied to the Inverting terminal and output is fed-back to the inverting terminal as voltage shunt feed-back. In this circuit, Op-Amp operates in the closed loop. Output equation of Non-Inverting Amplifier Simulation of Op-Amp as Non-Inverting Amplifier But, Non-Inverting configuration cannot give gain less than or equal to unity. The output varies according to the gain of the amplifier circuit up to V sat. Below are the circuit diagrams for Single as well as Dual voltage supply conditions. The polarity of the output voltage is same as that of the input. Input is applied to Non-Inverting terminal and output is fed-back to the Inverting terminal as a voltage shunt feed-back. In this circuit, Op-Amp operates in a closed loop. When V+ < V- the output=4V which is Logic High state. The voltage at the Non-Inverting and Inverting terminals (pins) i.e., V+ and V- are compared, and if V+ > V- then output is +V sat and if V+ V- the output=1.49V which is Logic Low state. The basic application of an Op-Amp is to use it as a voltage comparator. Some of the basic operation modes and application circuits are presented here.ħ41 Op-Amp description in Proteus Op-Amp as a Comparator The frequency of operation, slew rate and voltage ranges are the key parameters to select the right Op-Amp. For example:- 741 has single Op-Amp and LM 324, LM 339 have 4 Op-Amps each. Op-Amps in different IC packages are available.
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