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The  Operational Amplifier  or  Op-amp  for short, is a very versatile device that can be used in a variety of different electronic circuits and applications, from voltage amplifiers, to filters, to signal conditioners. But one very simple and extremely useful op-amp circuit based around any general purpose operational amplifier is the Astable Op-amp Multivibrator. We saw in our tutorials about  Sequential Logic  that multivibrator circuits can be constructed using transistors, logic gates or from dedicated chips such as the  NE555 timer . We also saw that the astable multivibrator switches continuously between its two unstable states without the need for any external triggering. But the problem with using these components to produce an astable multivibrator circuit is that for transistor based astables, many additional components are required, digital astables can generally only be used in digital circuits, and the use of a 555 timer may not ...

We have seen that we can connect resistors to a basic operational amplifier to produce various inverting and non-inverting outputs and configurations along with their respective gains. So to make things a little bit easier for all, here is a list of some of the “Basic Operational Amplifier Building Blocks” we can use to create different electronic circuits and filters. The Voltage Follower The Voltage Follower, also called a buffer dose not amplify or invert the input signal but instead provides isolation between two circuits. The input impedance is very high while the output impedance is low avoiding any loading effects within the circuit. As the output is connected back directly to one of the inputs, the overall gain of the buffer is  +1 and  Vout = Vin . The Voltage Follower Op-amp Circuit   The Op-amp Inverter The Inverter, also called an inverting buffer is the opposite to that of the previous voltage follower. The inverter does not amplify if ...

Here, the position of the capacitor and resistor have been reversed and now the reactance,  Xc  is connected to the input terminal of the inverting amplifier while the resistor,  Rƒ  forms the negative feedback element across the operational amplifier as normal. This operational amplifier circuit performs the mathematical operation of  Differentiation , that is it “ produces a voltage output which is directly proportional to the input voltage’s rate-of-change with respect to time “. In other words the faster or larger the change to the input voltage signal, the greater the input current, the greater will be the output voltage change in response, becoming more of a “spike” in shape. As with the integrator circuit, we have a resistor and capacitor forming an  RC Network across the operational amplifier and the reactance (  Xc  ) of the capacitor plays a major role in the performance of a  Op-amp Differentiator . Op-amp Differentiator Cir...

But what if we where to change the purely resistive (  Rƒ  ) feedback element of an inverting amplifier to that of a frequency dependant impedance, (  Z  ) type complex element, such as a  Capacitor, C . What would be the effect on the op-amps output voltage over its frequency range. By replacing this feedback resistance with a capacitor we now have an  RC Network connected across the operational amplifiers feedback path producing another type of operational amplifier circuit commonly called an  Op-amp Integrator  circuit as shown below. Op-amp Integrator Circuit As its name implies, the  Op-amp Integrator  is an operational amplifier circuit that performs the mathematical operation of  Integration , that is we can cause the output to respond to changes in the input voltage over time as the op-amp integrator produces an  output voltage which is proportional to the integral of the input voltage . In other words the ...

Thus far we have used only one of the operational amplifiers inputs to connect to the amplifier, using either the “inverting” or the “non-inverting” input terminal to amplify a single input signal with the other input being connected to ground. But as a standard operational amplifier has two inputs, inverting and no-inverting, we can also connect signals to both of these inputs at the same time producing another common type of operational amplifier circuit called a  Differential Amplifier . Basically, as we saw in the first tutorial about operational amplifiers, all op-amps are “Differential Amplifiers” due to their input configuration. But by connecting one voltage signal onto one input terminal and another voltage signal onto the other input terminal the resultant output voltage will be proportional to the “Difference” between the two input voltage signals of  V 1  and  V 2 . Then  differential amplifiers  amplify the difference between two voltage...