VHF tuning diode — capacitance ratio and bias range
The BBY40,235 is a single VHF varactor diode from NXP, designed for voltage-controlled tuning in VCOs, filters, and phase-locked loops up to the VHF band. Its headline parameter is the capacitance ratio C3/C25 of 6.5 — the capacitance at 3V reverse bias divided by the capacitance at 25V. That ratio defines the usable tuning range: a higher ratio means the oscillator can sweep a wider frequency span for a given control-voltage swing. At 25V reverse bias and 1MHz, the diode presents 6pF of junction capacitance. That is the minimum capacitance in the tuning curve, setting the upper frequency limit of the tank circuit. The peak reverse voltage rating of 30V gives a 5V headroom above the 25V measurement point, so the designer can safely bias at 25V continuous without approaching breakdown.
Temperature range and package — where it fits
The SOT-23 surface-mount package is a standard three-lead footprint shared across the BB series; the small body keeps parasitic inductance low for VHF circuits.
Lifecycle and compliance — no LTB risk
ROHS3 compliance is confirmed, which means the part meets the current EU restriction on hazardous substances without requiring an exemption review.