Varactor Diode Calculator
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Diode Capacitance (farads): {{ calculatedDiodeCapacitance }}
Cutoff Frequency (Hz): {{ calculatedCutoffFrequency }}
Quality Factor: {{ calculatedQualityFactor }}
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Varactor diodes, also known as varicap diodes, are a type of semiconductor diode designed to act as a variable capacitor under the influence of an applied voltage. They are widely used in voltage-controlled oscillators, RF filters, and tunable circuits, where their capacitance can be adjusted by changing the reverse bias voltage across the diode.
Historical Background
The varactor diode was invented in the early 1950s as part of the quest for frequency-agile radio systems. It enabled the development of voltage-controlled oscillators, phase-locked loops, and other tunable RF circuits without moving parts, revolutionizing radio frequency design and applications.
Calculation Formula
The capacitance \(C\) of a varactor diode at a given reverse bias voltage \(V\) is calculated using the formula:
\[ C = \frac{C_0}{(1 + \frac{V}{V_b})^m} \]
Where:
- \(C_0\) is the diode capacitance at zero bias in farads.
- \(V_b\) is the barrier potential in volts.
- \(V\) is the applied reverse bias potential in volts.
- \(m\) is the modulation factor, typically between 0.5 and 2.
The cutoff frequency (\(f_c\)) and quality factor (\(Q\)) are calculated as follows:
\[ f_c = \frac{1}{2 \pi R_s C} \]
\[ Q = \frac{f_c}{F} \]
Where:
- \(R_s\) is the series resistance in ohms.
- \(F\) is the operating frequency in MHz.