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Regarding Digital ICs

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avi_e-

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Hi Friends,

Here is my question on IC chips.

Some digital circuits perform functions based on 0s & 1s.How does the Digital ICs know that the signal we give is 0 or 1? Will they have any voltage levels like for eg.

0 - 3V
1 - 6V ?

Note the eg given is only to understand. If that is the case, how does it step down or step up i.e., regulate the voltage?

Thanking You in advance,
Avinash.S.
 

Hi

The digital ICs doesn't really know, the levels are implicit with the circuit behavior. In the case of TTL (a classical family), circuits operate with a 5 volt power supply. A TTL signal is defined as "low" or L when between 0V and 0.8V with respect to the ground terminal, and "high" or H when between 2.0V and 5V.

These levels are not arbitrary, they are caused because of the saturation and cut-off levels of the transistors inside the IC's circuitry.

Also note that exists a "prohibited zone"; in this zone the transistors aren't in saturation or cut-off zone, but in "direct mode". This mode uses the transistor as an amplifier (analog ciruits), not as a swtich(digital ciruits)

Best regards
 

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    avi_e-

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The two states of a wire are usually represented by some measurement of an electrical property: Voltage is the most common, but current is used in some logic families. A threshold is designed for each logic family. When below that threshold, the wire is "low," when above "high." Digital circuits establish a "no man's area" or "exclusion zone" that is wider than the tolerances of the components. The circuits avoid that area, in order to avoid indeterminate results.

It is usual to allow some tolerance in the voltage levels used; for example, 0 to 2 volts might represent logic 0, and 3 to 5 volts logic 1. A voltage of 2 to 3 volts would be invalid and would occur only in a fault condition or during a logic level transition, as most circuits are not purely resistive, and therefore cannot instantly change voltage levels. However, few logic circuits can detect such a fault, and most will just choose to interpret the signal randomly as either a 0 or a 1.

The levels represent the binary integers or logic levels of 0 and 1. In active-high logic, "low" represents binary 0 and "high" represents binary 1. Active-low logic uses the reverse representation.
Click to expand...

Some examples of digital levels here
http://www.interfacebus.com/voltage_threshold.html

Your question mix the analog circuits and the digital ones.
To convert a voltage we are using analog circuits, not a digital one.
 

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    avi_e-

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@TwinT : The "direct mode" you speak of is actually called "active mode".

Where did you get the term "direct mode". ?
 

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    avi_e-

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