BB208-03,115 - 10V Varactor Diode SOD-323 | NXP Semiconductors
MPN: BB208-03,115 ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $0.15 | $0.15 |
| 10 | $0.13 | $1.30 |
| 100 | $0.11 | $11.00 |
| 500 | $0.09 | $45.00 |
| 1,000 | $0.08 | $80.00 |
BB208-03,115 Overview
A varactor diode, also called a varicap or variable capacitance diode, is a semiconductor device that exploits the voltage-dependent depletion-layer capacitance of a reverse-biased PN junction. Within the hierarchy of diodes, it belongs to the family of RF and tuning diodes, used as a voltage-controlled capacitor rather than a rectifier. Its capacitance decreases as reverse bias increases, enabling electronic tuning of LC resonant circuits without any moving parts.
The BB208-03 is fabricated using NXP planar technology, which provides tight capacitance distribution and stable tuning characteristics over life and temperature. Key differentiating parameters include a maximum junction capacitance Cd of 23.2 pF at low reverse bias, an average forward current rating of 20 mA, and a wide operating temperature range of -55°C to +125°C, making it suitable for both consumer and industrial RF environments. The small SOD-323 body measures roughly 1.7 mm x 1.25 mm x 0.95 mm with a 1.3 mm lead pitch, supporting high-density PCB layouts.
Because the device is optimized for low-voltage operation, it pairs naturally with battery-powered and low-supply-voltage tuning circuits where higher-voltage varactors cannot reach their tuning range.
Typical applications include VCO (voltage-controlled oscillator) tuning in RF transceivers, electronically tuned LC filters, antenna impedance matching networks, and frequency modulation circuits in communications equipment.
Design-wise, keep the tuning voltage well within the 10 V reverse rating, use high-value series resistors to isolate the tuning node from oscillator noise, and account for the capacitance-temperature drift of the planar junction in narrow-band designs.
This page synthesizes distributor availability data, verified datasheet parameters, and practical design guidance for the BB208-03,115 not consolidated on the manufacturer product page.
Drop-in alternatives for BB208-03,115 — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with BB208-03,115 (same form factor and footprint) — differing in Device Type, Operating Temperature Range, Package, Terminal Form.
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Request AlternativesBB208-03,115 Maximum Ratings & Electrical Characteristics
| Device Type | Variable capacitance diode (varactor) |
| Configuration | Single |
| Repetitive Peak Reverse Voltage (VRRM) | 10 V |
| Junction Capacitance Cd @ 7.5 V, 1 MHz | 5.4 pF |
| Capacitance Ratio (C1/C7.5) | 5.2 |
| Max Junction Capacitance Cd @ Vr, f | 23.2 pF |
| Average Forward Current (IF(AV)) | 20 mA |
| Operating Temperature Range | -55°C to +125°C |
| Technology | Planar |
| Package | SOD-323 (SC-76) |
| Package Dimensions | 1.7 mm x 1.25 mm x 0.95 mm |
| Lead Pitch | 1.3 mm |
| Number of Terminals | 2 |
| Terminal Form | Gull Wing |
| Mounting Type | Surface Mount |
| Packing / Ordering Suffix | ,115 (standard packing) |
BB208-03,115 Pin Configuration
| Pin 1 | Cathode — Cathode terminal - reverse bias is applied here relative to anode; polarity marking per device body marking |
| Pin 2 | Anode — Anode terminal of the varactor junction |
Typical Applications
BB208-03,115 is suitable for 6 applications: VCO Tuning in RF Transceivers, Electronically Tuned LC Filters, Antenna Impedance Matching Networks, FM Modulation Circuits, Battery-Powered Tuners and Low-Voltage Radios, Test and Measurement Instrumentation.
VCO Tuning in RF Transceivers
The BB208-03,115 fits VCO tank circuits because its low-voltage C-V characteristic (5.4 pF at 7.5 V, ratio 5.2) allows a full tuning span from control voltages generated by low-voltage DACs or charge pumps. Placed across the inductor in the LC resonator, the diode's capacitance shifts the oscillation frequency as the tuning voltage varies. Because the planar junction has a smooth, repeatable C-V curve, frequency-versus-voltage linearity is predictable, easing calibration. Keep the DC tuning node isolated with a high-value series resistor (tens of kohms) so oscillator phase noise does not modulate the diode, and use bypass capacitors to decouple the tuning line without loading the RF tank.
Recommended
Electronically Tuned LC Filters
Variable capacitance diodes like the BB208-03,115 enable voltage-controlled bandpass and low-pass filters where fixed capacitors cannot track changing channel assignments. With 23.2 pF maximum Cd at low bias dropping to about 5.4 pF near 7.5 V, a single diode can swing a filter center frequency over a useful range without relays or switched capacitor banks. The 10 V reverse rating and -55°C to +125°C operating range suit industrial RF front ends. Design consideration: the effective Q of the varactor adds series loss to the tank, so narrow high-Q filters should budget insertion loss and verify the bias network does not shunt RF, typically via RF chokes or large-value resistors.
Recommended
Antenna Impedance Matching Networks
In portable and IoT transmitters, antenna impedance shifts with enclosure, hand position, and proximity effects. The BB208-03,115 provides electronically variable shunt capacitance in Pi- and L-match networks, letting a controller retune the match in real time as load conditions change. Its small SOD-323 footprint (1.7 mm x 1.25 mm) allows placement directly at the antenna feed point, and the 20 mA forward current rating and 10 V reverse rating handle typical RF swing levels in sub-watt transmitters. Because varactor capacitance is bias-dependent, a clean, well-bypassed tuning voltage supply directly determines match stability; ripple on this rail appears as unintended frequency or match modulation.
Recommended
FM Modulation Circuits
Applying an audio or data modulation signal to the tuning node of a varactor-loaded oscillator produces direct frequency modulation. The BB208-03,115's monotonic, low-hysteresis planar C-V characteristic translates modulation voltage into proportional frequency deviation, which is the core mechanism in FM transmitters, wireless microphones, and telemetry links. With a capacitance ratio of 5.2 across the 0 V to 7.5 V control range, modest modulation voltages yield usable deviation around a stable center frequency. Designers should bias the diode in the mid-range of its C-V curve, where dC/dV is most linear, to minimize modulation distortion, and AC-couple the modulation source into the DC bias point.
Recommended
Battery-Powered Tuners and Low-Voltage Radios
The BB208-03 family is explicitly characterized as a low-voltage variable capacitance diode, making it appropriate for single-cell and low-rail consumer radios where classic 20 V to 30 V varactors cannot be biased into their tuning range. At a 5 V or 3.3 V rail the BB208-03,115 still delivers a meaningful capacitance swing (several picofarads), preserving electronic tuning without a boost converter. Quiescent current of the tuning network is essentially zero because the diode is reverse biased, which preserves battery life. The main trade-off is reduced tuning ratio at low bias voltages, so receiver designers should verify channel coverage at the minimum available rail voltage before committing to the design.
Recommended
Test and Measurement Instrumentation
In signal generators, sweep oscillators, and alignable IF strips, varactor tuning removes hand-adjusted trimmer capacitors and enables automated, repeatable factory calibration. The BB208-03,115's stable planar construction and -55°C to +125°C rating support instrument-grade frequency accuracy across environmental conditions. A calibration routine can store tuning-voltage-to-frequency tables in memory, compensating for unit-to-unit capacitance spread within the datasheet distribution. Because the diode's capacitance drifts slightly with temperature, precision instruments may pair the varactor with a temperature sensor and lookup-table correction. The SOD-323 package's predictable parasitics (roughly sub-nH lead inductance) simplify simulation of the resonator in RF design tools.
Recommended
Recommended Products Summary
Engineering reference data for BB208-03,115 — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | BB208-02,115 |
|---|---|---|
| Package | SOD-323 (SC-76) | SOD-523 (SC-79) - smaller, NOT pin-compatible |
| Brand | NXP Semiconductors | NXP Semiconductors |
| Reverse Voltage (VRRM) | 10 V | 10 V |
| Operating Temperature | -55°C to +125°C | -55°C to +125°C |
Key Differentiators
- Low-voltage optimization (vs Higher-voltage varactor families (e.g., 20-30 V rated tuning diodes))
- Same silicon in two footprints (vs BB208-02,115)
- Wide industrial temperature range (vs Typical consumer-grade tuning diodes)
Design Notes
Isolate the varactor tuning node from RF and noise with a high-value series resistor (typically 10 kohm to 100 kohm) between the control voltage source and the diode cathode. Any noise or ripple on the tuning rail directly frequency-modulates the oscillator, degrading phase noise. Add local RF bypassing (e.g., 10 nF at the bias node) so tuning-voltage transients do not couple into the tank, while ensuring the bypass does not swallow the modulation signal in FM applications.
Estimated: keep the instantaneous reverse voltage across the BB208-03,115 below the 10 V VRRM rating under worst-case conditions, including RF swing superimposed on the DC bias. For example, with 8 V DC bias and a tank that swings +/-1.5 V at the diode, the peak reverse voltage approaches 9.5 V - only 0.5 V margin. Derating the tuning rail to 7 V to 8 V preserves reliability and still covers most of the useful 5.2:1 capacitance ratio.
Do not assume a varactor's nominal capacitance defines the tuning range - always design from the datasheet C-V curve. At very low reverse bias the BB208-03's capacitance approaches its 23.2 pF maximum with high dC/dV, which makes the oscillator very sensitive to bias error and temperature. Bias in the mid-curve region for linearity. Also verify the varactor's effective Q at your operating frequency, since junction losses add insertion loss to high-Q filters.
Compliance Information
Compliance status not stated in retrieved web data; the ,115 ordering suffix conventionally indicates RoHS-compliant lead-free packing for NXP parts, but this must be confirmed on the official NXP product page.
