The above drawn circuit is a 2-input CMOS NAND gate. Now let's understand how this circuit will behave like a NAND gate. The circuit output. For this reason, it is inadvisable to allow a CMOS logic gate input to float under any For example, here is the schematic diagram for a CMOS NAND gate. In digital electronics, a NAND gate (NOT-AND) is a logic gate which produces an output which NAND gates are basic logic gates, and as such they are recognised in TTL and CMOS ICs. This schematic diagram shows the arrangement of  ‎Symbols · ‎Implementations.


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Fortunately, there is an easy solution to this dilemma, one that is used frequently in CMOS cmos nand gate circuitry. Again, the cmos nand gate for a pulldown resistor is not critical: Because open-collector TTL outputs always sink, never source, current, pullup resistors are necessary when interfacing such an output to a CMOS gate input: Although the CMOS gates used in the preceding examples were all inverters single-inputthe same principle of pullup and pulldown resistors applies to multiple-input CMOS gates.

NAND gate - Wikipedia

Of course, a separate pullup or pulldown resistor will be required for each gate input: This brings us to the next question: Not surprisingly, the answer s to this question cmos nand gate a simplicity of design much like that of the CMOS inverter over its TTL equivalent.

Notice how transistors Q1 and Q3 resemble the series-connected complementary cmos nand gate from the inverter circuit. The upper transistors of both pairs Q1 and Q2 have their source and drain terminals paralleled, while the lower transistors Q3 and Q4 are series-connected.

The following sequence of illustrations shows the behavior of this NAND gate for all four possibilities of input logic levels 00, 01, 10, and All that needs to be added is another stage of transistors to invert the output signal: Instead of two paralleled sourcing upper transistors connected to Vdd and two series-connected sinking lower transistors connected to ground, the NOR gate uses two series-connected sourcing transistors and two parallel-connected sinking transistors like this: Each pair is controlled by a single input signal.

This behavior, of course, defines the NOR logic function.

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In this measure of performance, CMOS is the unchallenged victor. Because cmos nand gate complementary P- and N-channel MOSFET pairs of a CMOS gate circuit are ideally never conducting at the same time, there is little or no current drawn by the circuit from the Vdd power supply except for what current is necessary to source current to a load.

TTL, on the other hand, cannot function without some current drawn at cmos nand gate times, due to the biasing requirements of the bipolar transistors from which it is made.

Then the transistor becomes active and the output of cmos nand gate transistor is shorted to ground which gives LOW output. Same way in all the other conditions one or two diodes will be forward biased resulting in shorting the V to ground.

NAND gate operation

No voltage is applied to transistor base terminal and transistor will be in cut off. So, Vout will not find any path to get connected with Vdd.

Since, the path to ground is established, Vout will be discharged; so, Low. In all the 4 cases we have observed that Vout is following the exact pattern as in the truth table for the cmos nand gate input combination.

NAND and NOR gate using CMOS Technology – VLSIFacts

No path from Vout to GND. Therefore, no discharging and hence Vout will be High.


So, Vout would get discharged and will be at level Low.

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