The KVX38S2-23-0 is a single silicon varactor (tuning) diode in a SOT-23-3 surface-mount package. It is designed for voltage-controlled tuning in RF circuits — VCOs, phase-locked loops, and filter banks — where a variable capacitance controlled by a DC bias voltage is needed. The key parameters that define its tuning range are the 32 pF capacitance at 3 V and the 27 V peak reverse voltage, which together set the capacitance swing available for the application.
32 pF at 3 V — the tuning capacitance that sets the frequency range
At a reverse bias of 3 V and a test frequency of 1 MHz, the KVX38S2-23-0 measures 32 pF. This is the capacitance value you use when calculating the resonant frequency of the LC tank in a VCO or the cutoff in a tunable filter. The 27 V peak reverse rating tells you the maximum bias voltage you can apply, which determines how far the capacitance can be reduced (typically to a few picofarads at high bias). For a design targeting a specific frequency band, the 32 pF at 3 V is the starting point for the tuning curve.
A Q (quality factor) of 200 at 4 V reverse bias and 50 MHz tells you the varactor has low series resistance and will not heavily damp the resonator. In a VCO tank circuit, a Q of 200 keeps the phase noise low and the oscillator stable. If the Q were significantly lower, the tank would lose energy each cycle, widening the oscillator's spectral line. For a 50 MHz IF filter or a VCO in that range, this Q is adequate for most commercial and industrial designs.
Temperature range and package — built for harsh environments
The SOT-23-3 package (also known as TO-236-3 or SC-59) is a standard three-lead surface-mount footprint that reflows easily and fits compact RF layouts. The device is ROHS3 compliant.
For a BOM line, this removes the supply risk of an obsolete part.