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Minimum High Input Voltage (Vih) is defined as the minimum input voltage at the high logic level inside a CMOS circuit. It represents the lowest voltage that will be recognized as a logical high input by the digital circuit.
The calculator uses the formula:
Where:
Explanation: The formula calculates the minimum input voltage required for a high logic level by subtracting the high noise margin from the minimum high output voltage.
Details: Accurate Vih calculation is crucial for ensuring proper signal integrity and noise immunity in digital circuits. It helps designers verify that the output of one logic gate can properly drive the input of another gate under worst-case conditions.
Tips: Enter Minimum High Output Voltage (Voh) and High Noise Margin (Nh) in volts. Both values must be positive numbers. The calculator will compute the Minimum High Input Voltage (Vih).
Q1: What is the significance of Vih in digital circuits?
A: Vih ensures that the input signal is reliably recognized as a logic high, preventing misinterpretation of signal levels and ensuring proper circuit operation.
Q2: How does noise margin affect Vih?
A: The noise margin provides a safety buffer that allows the circuit to tolerate noise and signal degradation while still correctly interpreting the logic level.
Q3: What are typical values for Voh in CMOS circuits?
A: For standard CMOS circuits, Voh is typically close to the supply voltage (e.g., 4.9V for a 5V supply), but exact values depend on the specific technology and loading conditions.
Q4: Why is Vih important for interface design?
A: Vih is critical when connecting different logic families or when designing interfaces between circuits to ensure compatibility and reliable data transmission.
Q5: How does temperature affect Vih?
A: Temperature variations can affect transistor characteristics, which may cause slight changes in Vih values. Datasheets typically provide Vih specifications over temperature ranges.