Output Voltage of Op Amp with V+ 2.5V & V- Not Connected

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Discussion Overview

The discussion revolves around the output voltage of an operational amplifier (op-amp) when the non-inverting input (V+) is set to 2.5 volts and the inverting input (V-) is not connected. Participants explore the implications of this configuration, particularly focusing on the relationship between V-, Voutput, and the resistor connecting them.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant suggests that this is a non-inverting op-amp configuration with a gain of one, often referred to as a voltage follower.
  • Another participant claims the output voltage is +2.5 volts.
  • A question is raised about the voltage at V- since it is not connected, asking whether it is zero or +2.5 volts like V+.
  • A further inquiry is made regarding the connection of V- to Voutput through a resistor and the implications of this setup, including considerations of voltage drop and input bias current.
  • Reference to external material is provided to support the discussion, suggesting to consider the resistor R as having infinite resistance.

Areas of Agreement / Disagreement

Participants express differing views on the behavior of V- and its implications for Voutput, indicating that multiple competing perspectives remain without a clear consensus.

Contextual Notes

The discussion includes assumptions about the behavior of the op-amp in this specific configuration, the role of the resistor, and the effects of input bias current, which are not fully resolved.

mohamad hajj
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suppose an amplifier with V+ is 2.5 volts
and V- is not connected...V- and Voutput are connected by a resistor.
what is the voltage on the outpout of the op amp?
 
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This is a non-inverting op-amp configuration with a gain of one, sometimes called a voltage follower.

Bob S
 
+2.5v.
 
the V- is not connected. (even not connected to ground reference)
the voltage at V- is zero or +2.5 volts like V+ or what?
thank you
 

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