Electronic – how to solve this op-amp circuit

circuit analysishomeworkmathoperational-amplifier

I would appreciate some help solving this simple circuit which I'm trying for some time but can't seem to match with the given answer.
Aim is to find output voltage \$V_o\$

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for the given input voltage –

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My attempt : Since the only current flow \$i\$ is from \$V_O\$ to ground via 4k and 1k resistors, and \$V_+=V_{in}\$ $$i(mA)=V_{in}/1$$
$$\Rightarrow V_o=V_{in}+i*4=5V_{in}$$

So that when \$V_{in}\$ vary from (-5 to -2); (-2 to 2); (2 to 5)., \$V_o\$ saturates at -10; varies linearly to 10; then saturates at 10.

But the output is given as –

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Thanks,

Best Answer

Your circuit doesn't have negative feedback: -

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Therefore it acts as a comparator with hysteresis and hence, the output changes state when the input voltage passes the hysteresis threshold points shown below in red dots: -

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The non-inverting version is also known as a Schmitt trigger circuit: -

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