BB208-02,135 - 10V Low Voltage Varactor Diode | NXP Semiconductors
MPN: BB208-02,135 β Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $0.16 | $0.16 |
| 10 | $0.16 | $1.60 |
| 100 | $0.15 | $15.00 |
| 500 | $0.14 | $70.00 |
| 1,000 | $0.13 | $130.00 |
BB208-02,135 Overview
A varactor diode, also called a variable capacitance diode or varicap, is a semiconductor device that exploits the voltage-dependent depletion-layer capacitance of a reverse-biased PN junction. Within the power and signal-chain hierarchy, it belongs to the discrete semiconductor family and functions as a voltage-controlled capacitor for tuning circuits, sitting alongside other RF passives such as inductors and fixed capacitors in the front end of tuners, oscillators and filters.
Key features of the BB208-02 include excellent CV linearity for predictable tuning curves, a high capacitance ratio enabling wide tuning ranges from a small control-voltage swing, and very low series resistance which preserves Q factor in resonant circuits. The ultra-small SOD-523 footprint conserves PCB area in compact RF assemblies such as antenna tuners and VCO modules.
Technically, the planar epitaxial structure provides a sharp, repeatable junction profile, delivering a smooth capacitance-versus-voltage characteristic that simplifies linearizing circuitry in PLL-based frequency synthesizers. Distributor listings such as Utmel and FindIC confirm the single-diode configuration, 2 terminations and dual flat terminal form.
Typical applications include voltage-controlled oscillators (VCOs), electronically tuned LC filters, RF tuner bandpass circuits, and PLL loop tuning elements in communication equipment operating at low supply voltages.
In design, keep the tuning-voltage source low-noise and well decoupled, since varactor bias noise appears directly as oscillator phase noise; also observe the 10 V peak reverse voltage limit.
This page synthesizes distributor pricing, availability, and drop-in alternative analysis not found in the manufacturer datasheet, providing an engineering-oriented selection resource.
Drop-in alternatives for BB208-02,135 β same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Quick Comparison Tool β Select alternative parts for side-by-side comparison:
BB208-02,115
β Drop-Inβ In Stock
$0.1637 / Unit
View Datasheet βBB208-02,125
β Drop-In β οΈ εζ°εΎ ιͺθ―π Reference alternative (not in catalog)
BB208-02,135 Maximum Ratings & Electrical Characteristics
| Device Type | Variable capacitance diode (varactor) |
| Configuration | Single diode |
| Maximum Reverse Voltage | 10 V |
| Nominal Capacitance | 5.4 pF @ 7.5 V, 1 MHz |
| Capacitance Ratio | 5.2 (C1/C7.5) |
| Continuous Forward Current | 20 mA |
| Diode Capacitance (Ct) | 19.9 pF |
| Technology | Planar silicon |
| CV Linearity | Excellent (per datasheet) |
| Operating Temperature Range | -55C to +125C |
| Package | SOD-523 (SC-79) SMD plastic |
| Number of Pins | 2 |
| Mounting Type | Surface Mount |
| Packaging | Tape & Reel (7 inch reel) |
| Minimum Order Quantity | 3000 |
BB208-02,135 Pin Configuration
| Pin 1 | Cathode β Cathode terminal - connect to tuning (reverse bias) voltage node |
| Pin 2 | Anode β Anode terminal - connect to RF tank circuit node |
Typical Applications
BB208-02,135 is suitable for 6 applications: Voltage-Controlled Oscillators (VCOs), PLL Frequency Synthesizers, Electronically Tuned LC Filters, RF Tuner Front Ends, Antenna Matching / Tuning Networks, Test and Measurement Instruments.
Voltage-Controlled Oscillators (VCOs)
The BB208-02,135 is well suited to VCO tank circuits because its 5.2 capacitance ratio (C1/C7.5) gives a wide frequency-tuning range from a modest 0-10 V control swing, and its very low series resistance preserves tank Q for low phase noise. In a typical LC VCO, the varactor is DC-biased at its cathode via a 47k resistor and AC-coupled into the inductor tank with a 1-10 nF blocking capacitor. Because its 5.4 pF mid-bias capacitance keeps the tank impedance manageable at VHF/UHF frequencies, designers achieve tuning slopes compatible with PLL charge-pump outputs. The excellent CV linearity of the planar structure also simplifies loop-gain compensation across the tuning band.
Recommended
PLL Frequency Synthesizers
In PLL-based frequency synthesizers, the BB208-02,135 acts as the tuning element that converts charge-pump error voltage into oscillator frequency correction. Its excellent CV linearity means loop gain varies less across the band, easing loop-filter design and maintaining stable bandwidth. The 10 V maximum reverse voltage accommodates charge pumps operating from higher rails, while the -55C to +125C junction range covers industrial synthesizer environments. Placed directly across the VCO tank inductor with a 10-100k bias resistor, the varactor's low series resistance minimizes added phase-noise degradation. The SOD-523 package keeps parasitic inductance low, which matters for UHF bands where even 1 nH of series inductance shifts the tuning curve.
Recommended
Electronically Tuned LC Filters
Varactors such as the BB208-02,135 enable voltage-programmable bandpass and lowpass filters by replacing mechanical or switched capacitor banks. The 5.2 capacitance ratio allows roughly a 2x shift in filter corner frequency across the 1-7.5 V bias range, while excellent CV linearity keeps passband shape predictable as tuning voltage changes. Its very low series resistance limits the insertion-loss penalty in high-Q LC resonators. In design, place the varactor in series with the filter inductor and couple the control node through a large-value resistor so RF swing does not rectify across the junction. The SOD-523 footprint supports dense filter arrays in channelized receivers and test equipment.
Recommended
RF Tuner Front Ends
Low-voltage tuner front ends for broadcast receivers use varactors like the BB208-02,135 to tune input bandpass and local-oscillator stages from a common control voltage. The device's high capacitance ratio covers wide band segments without band switching, and the 10 V rating matches standard tuner tuning rails. NXP's low-voltage design intent means the CV curve is optimized for tuning voltage sources derived from 5 V or 12 V supplies with simple dividers. The ultra-small SOD-523 package suits compact module tuners where board area is constrained. Because front-end Q directly affects image rejection, the varactor's low series resistance is a key selection parameter in these designs.
Recommended
Antenna Matching / Tuning Networks
Adaptive antenna matching networks use varactors to keep antenna VSWR optimized across frequency, load, and hand-position changes in portable and IoT radios. The BB208-02,135 provides voltage-controlled reactance in pi or L matching sections; its 5.4 pF nominal capacitance and 5.2 ratio give sufficient matching-range coverage for compact antennas operating in VHF through UHF bands. Low series resistance is critical here because matcher loss directly reduces transmitter efficiency and battery life. The -55C to +125C operating range tolerates outdoor and vehicular environments. Control circuits should be noise-filtered, since bias noise modulates the match and can create spurious emissions in adjacent channels.
Recommended
Test and Measurement Instruments
Signal generators, sweep oscillators, and tracking generators in test equipment employ varactors like the BB208-02,135 for electronically swept tuning. The planar device's repeatable, low-hysteresis CV characteristic ensures calibration stability between service intervals, and its -55C to +125C range survives instrument warm-up and harsh lab transport conditions. Sweep circuits can drive the varactor from 0 V to just under 10 V for maximum span, with the 5.2 ratio delivering greater than an octave of frequency coverage in a simple LC oscillator. Very low series resistance supports the high-Q tanks needed for low close-in phase noise in reference-grade sources. SOD-523 mounting simplifies automated assembly of oscillator modules.
Recommended
Recommended Products Summary
Engineering reference data for BB208-02,135 β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | BB208-02,115 | BB208-02,125 |
|---|---|---|---|
| Package | SOD-523 (SC-79) | SOD-523 (SC-79) - same | SOD-523 (SC-79) - same |
| Brand | NXP Semiconductors | NXP Semiconductors | NXP Semiconductors |
| Configuration | Single varactor | Single varactor | Single varactor |
| Maximum Reverse Voltage | 10 V | 10 V | 10 V |
| Diode Capacitance (Ct) | 19.9 pF | 19.9 pF | 19.9 pF |
| Capacitance Ratio | 5.2 (C1/C7.5) | 5.2 (C1/C7.5) | 5.2 (C1/C7.5) |
| Operating Temperature | -55C to +125C | -55C to +125C | -55C to +125C |
Key Differentiators
- High capacitance ratio of 5.2 for wide tuning range (vs BB208-03,115)
- Excellent CV linearity simplifies PLL loop design (vs Generic varactor substitutes)
- Ultra-small SOD-523 footprint saves board area (vs BB208-03,115 (SOD-323))
Design Notes
Tuning-voltage noise appears directly as oscillator phase noise because any ripple on the BB208-02,135 bias modulates its junction capacitance. Filter the control line with an RC network (e.g., 10k series resistor plus 100 nF to ground) placed close to the varactor cathode, and keep high-frequency digital traces away from the tuning node. Use a low-noise reference or DAC output for the tuning source; a charge-pump PLL output should pass through a loop filter sized for low spurious content.
Respect the 10 V maximum reverse voltage: transient excursions above breakdown damage the junction and permanently alter the CV curve. Also ensure the RF swing across the diode does not forward-bias it on negative peaks - keep peak-to-peak tank voltage below roughly twice the DC bias to avoid rectification distortion and harmonics. Large RF swings cause capacitance pumping, generating sidebands in VCOs. If needed, split the tank with two series varactors to halve per-device RF stress.
Minimize series inductance by placing the BB208-02,135 directly across the tank inductor pads; at UHF even the small SOD-523 parasitics (~0.5-1 nH) shift the tuning characteristic. Keep ground return paths short and connect the anode side to a solid RF ground plane. Because this part is a maturing product with 99-week factory lead time, add a second footprint-compatible pad pattern (identical SOD-523) so the BB208-02,115 or a verified equivalent can be substituted without PCB respin.
Compliance Information
Compliance status was not stated in the provided web data. NXP typically marks the ,135 suffix as RoHS-compliant (suffix code convention), but this must be confirmed against the official NXP compliance documentation before assuming.
