# Question regarding opamp

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#### Manchested

##### Member level 5 Hi, I am new to electronics. I would like to ask a few questions about opamp.

1. Does opamp provide constant current or constant voltage?
2. What will happen to the voltage across and current through a resistive load if it is connected to the opamp's output? Will the voltage always stay the same while current is changing?
3. What will happen if the the resistance of the load is approximately equal to the opamp output impedance? if says an opamp has 100ohms O/I, does the load has to be a lot larger to have the max voltage drop across it?

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#### Miguel Gaspar

##### Advanced Member level 1 The op-amp was primary designed to be an amplifier, and has the hability to amplify correctly the imput signal from -I to +I accordily the datasheet specifications.

2. ifyour input signal is 1v and your gain is for example 4, your output will be 4V and your current 4V/100 Ohms = 0.04A

3. the Vout / RL = I max and must not be greater than the maximum current allowed by the device. Fir example the datasheet, Lm741 = 25mA and if your Vout = 10v, rMAX = 10v/25mA = 400 Ohms, thata means that you can put a Rl greater or equal to 400 Ohms.

• Manchested

### Manchested

Points: 2

#### Manchested

##### Member level 5 For Q1, If a load is connected to the output, will the current changes when the resistance of load increase or decrease? or it's the voltage that changes? or it's depending on the output impedance and topology of the opamp?

For Q2, do you mean the load = 100 ohms or the output impedance is?

For Q3, Shouldn't Rmax be called Rmin instead if only 400 ohms or above could work?

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#### Miguel Gaspar

##### Advanced Member level 1 For Q1 The op-amp is an amplifier if you have a signal of 10V and an gain of 1, your output will be 10V that is true if you have no load, nothin conected to the output od the opamp. If you have a Load conected to the output of the op-amp but that current in the load is less than the maximum current of the op-amp the output will be 10 V. But if the current try to be more than the maximum, Vout will not be 10V.

For Q2, if your input signal is 1v and your gain is for example 4, your output will be 4V, and if your RL = 1k Ohm your current will be 4V/1K Ohms = 0.004A. Rl is the resistance conected to the output and GND and is of 1,000 Ohms.

For Q3, Ok R min

• Manchested

Points: 2