How do you know what resistor to use in a circuit?

Resistor selection requires three steps:

1. Determine the resistance and the watts to be dissipated by the resistor.
2. Determine the proper “Watt Size” (physical size) as controlled by watts, volts, permissible temperatures, mounting conditions and circuit conditions.

Which of the following resistor value ranges are suitable for general purpose op amp circuits?

100 ohms and 1000 ohms are about the right range of high/low for a typical OP-amp.

What is the value of the input resistor an ideal op amp?

zero input
The ideal op amp has zero input current. This is because of infinite input resistance. As the input resistance of ideal op amp is infinite, an open circuit exists at input, hence current at both input terminals is zero.

Why do op amps need resistors?

Most op amps operating from a single supply voltage require several high quality external resistors to generate a local bias voltage—to optimize the DC operating-point—and resistors to set gain. In this circuit, the input resistors form a supply splitter for biasing and a net attenuation of 0.75.

How do you recognize an op-amp as an ideal op-amp?

An “ideal” or perfect operational amplifier is a device with certain special characteristics such as infinite open-loop gain AO, infinite input resistance RIN, zero output resistance ROUT, infinite bandwidth 0 to ∞ and zero offset (the output is exactly zero when the input is zero).

What is ideal op-amp?

Operational amplifier: The ideal op amp is an amplifier with infinite input impedance, infinite open-loop gain, zero output impedance, infinite bandwidth, and zero noise. It has positive and negative inputs which allow circuits that use feedback to achieve a wide range of functions.

How do you identify an op amp as an ideal op amp?

The so-called ideal op amp is to idealize various technical indicators of op amps, and it must have the following characteristics.

1. 1.1 Infinite Input Resistance.
2. 1.2 Zero Output Impedance.
3. 1.3 Infinite Open-loop Gain.
4. 1.4 Infinite Common-mode Rejection Ratio.
5. 1.5 Infinite Bandwidth.

What is the input resistor in an op amp?

All op amps have some input capacitance, both differential and common mode. If the op amp is connected as a follower and the impedances are balanced by putting a resistor in the feedback path, the system may become prone to oscillation. The input resistor was 470 kΩ, so the customer put a 470 kΩ in the feedback.

What happens if my resistor is too high?

The higher the resistance, the lower the current flow. If abnormally high, one possible cause (among many) could be damaged conductors due to burning or corrosion. All conductors give off some degree of heat, so overheating is an issue often associated with resistance.

How to choose resistors for discrete opamp?

For a discrete op-amp the quality of the resistors can be chosen, but get more expensive the better they are. One can also get matched pairs of gain resistors e.g. “Vishay Thin Film MPM Matched Pair Resistor Network provides ± 2 ppm/°C tracking and a ratio tolerance as tight as 0.01 \%”.

What is the value of the resistor in an inverting op amp?

For precision and lowest resistor noise the smaller value is often in the hundreds of ohms range. For lowest power use it may well be 100K or higher. For RF however it can be 50 ohms, or lower. In an inverting op-amp the first input resistor is summing into a virtual ground, so this sets the input impedance.

What is the input voltage of an op-amp?

The op-amp is inverting hence the inverting input is at 0 volts hence the output load IS the feedback resistor and you can’t have this too low or you won’t get the output voltage amplitude. On the other hand, you can’t go too big because the parasitic capacitances of the op-amp will start to reduce gain too much at higher frequencies.

How do you calculate the gain of a resistor?

The gain here is A = -R f /Rin. However, lets say I want a gain of 10 V/V. Which resistor value would you choose and why?