It isn't a NOT gate.

Your circuit can produce an inverting logic function. So it has the 'NOT' part - but not the 'logic gate' part. It's not a logic gate.

A logic gate includes the following properties:

• Is a standard block than can be cascaded with identical copies.

• A current gain of at least 2 (typically much higher). Its output must be able to drive multiple circuits of its own type.

Your circuit fails on both these.

To your questions...

(1) Why do we not consider this circuit and instead use transistors in practical NOT gate ICs?

To get:

• The high current gain, with high efficiency compared to passive circuits like diode-resistor logic.
• Much better LOW/HIGH output voltages that are closer to the rails.
• Much better LOW/HIGH input voltage thresholds that are well inside the LOW/HIGH output voltages of the same-type driving gate.

(2) Why can we not make NOT gates using diodes and resistors just like we do in OR and AND gates using Diode-Resistor Logic?

OR and AND gates don't invert the input signal's polarity. NOT gates do only that. Diode-resistor logic can't do inversions. So no NAND, NOR, XOR gates either.

It isn't a NOT gate.

Your circuit can produce an inverting logic function. So it has the 'NOT' part - but not the 'logic gate' part. It's not a logic gate.

A logic gate includes the following properties:

• Is a standard block than can be cascaded with identical copies.

• A current gain of at least 2 (typically much higher). Its output must be able to drive multiple circuits of its own type.

Your circuit fails on both these.

To your questions...

(1) Why do we not consider this circuit and instead use transistors in practical NOT gate ICs?

We use a transistor circuit to get:

• The high current gain, with high efficiency over passive circuits like diode-resistor logic.
• Much better LOW/HIGH output voltages that are closer to the rails.
• Much better LOW/HIGH input voltage thresholds that are well inside the LOW/HIGH output voltages of the same-type driving gate.

(2) Why can we not make NOT gates using diodes and resistors just like we do in OR and AND gates using Diode-Resistor Logic?

OR and AND gates don't invert the input signal's polarity. NOT gates do only that. Diode-resistor logic can't do inversions, so can't make NOT, or NAND, NOR, XOR gates either.

It isn't a NOT gate.

Your circuit can produce an inverting logic function. So it has the 'NOT' part - but not the 'logic gate' part. It's not a logic gate.

A logic gate includes the following properties:

• A standard block than can be cascaded with identical copies.

• A current gain of at least 2 (typically much higher). Its output must be able to drive multiple circuits of its own type.

Your circuit fails on both these.

To your questions...

(1) Why do we not consider this circuit and instead use transistors in practical NOT gate ICs?

Primarily to get the current gain, with high efficiency compared to passive circuits like diode-resistor logic.

(2) Why can we not make NOT gates using diodes and resistors just like we do in OR and AND gates using Diode-Resistor Logic?

OR and AND gates don't invert the input signal's polarity. NOT gates do only that. Diode-resistor logic can't do inversions. So no NAND, NOR, XOR gates either.

It isn't a NOT gate.

Your circuit can produce an inverting logic function. So it has the 'NOT' part - but not the 'logic gate' part. It's not a logic gate.

A logic gate includes the following properties:

• Is a standard block than can be cascaded with identical copies.

• A current gain of at least 2 (typically much higher). Its output must be able to drive multiple circuits of its own type.

Your circuit fails on both these.

To your questions...

(1) Why do we not consider this circuit and instead use transistors in practical NOT gate ICs?

To get:

• The high current gain, with high efficiency compared to passive circuits like diode-resistor logic.
• Much better LOW/HIGH output voltages that are closer to the rails.
• Much better LOW/HIGH input voltage thresholds that are well inside the LOW/HIGH output voltages of the same-type driving gate.

(2) Why can we not make NOT gates using diodes and resistors just like we do in OR and AND gates using Diode-Resistor Logic?

OR and AND gates don't invert the input signal's polarity. NOT gates do only that. Diode-resistor logic can't do inversions. So no NAND, NOR, XOR gates either.