gregorian operational amplifiers pdf
1. What is an Operational Amplifier ?
An Operational Amplifier is a device used in several electronic circuits and it simplifies the design of analog circuits because it can be treated as a block. An Op Amp has two inputs (first stage is a differential amplifier) and one output (in fact it can have more 2 supply pins and offset adjust pins). An Op Amp usually is set with a feedback loop from its output to one of its inputs (negative or positive feedback). Feedback is keyword to use an Op Amp properly, since it has a high gain in open loop but a small bandwidth (frequency response). When you set feedback, the bandwidth increases and the gain decreases (the relationship BW x Gain is constant). Op Amps also have very high input impedance and low output impedance, so it can be very useful to adjust impedances between circuits. The voltage gain can be easily set by adjusting the correct values of resistors in the loop feedback.
2. How is it made ?
It is made of transistors (bipolars or/and fets) packaged together in a integrated circuit. You can see the electrical schematic and the components in an Op Amp datasheets (a lot of transistors and other components). An Op Amp can be made of discrete components and in the past, they were built using electronic valves (tubes).
3. Why it has got that name ?
Operational Amplifier name derives from its application from the past: these amplifiers were invented to be used as part of ANALOG COMPUTERS to perform the MATH OPERATIONS (sum of voltages, subtraction of voltages, multiplication, etc). Since the fact that computation turned into digital system, Op Amps had other application in the modern world.
4. What are its applications ?
So many applications, mainly on instrumentation, audio, etc
Op Amps can be used as signal amplifiers (inverter or non inverter), as adder amplifier, subtractor amplifier, log amplifier, antilog amplifier, oscillator, schmitt trigger, comparator, integrator and differentiator amplifiers, part of A to D converter and D to A converter, buffers and many applications.
5. What are its limitations ?
Op Amps are very close to ideal devices (infinite input impedance, zero output impedance, very high gain, fast slew rate, high bandwidth, no offset in the output).
Their limitations are:
- Output voltage restricted to rail voltages (supply voltages)
- Minimum supply voltages
- Slew rate not infinite
- Bandwidth
- Power
- Temperature range