BB135,115 - 30V UHF Varactor Diode SOD-323 | NXP
MPN: BB135 β Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $0.07 | $0.07 |
| 10 | $0.06 | $0.60 |
| 100 | $0.05 | $5.00 |
| 500 | $0.045 | $22.50 |
| 1,000 | $0.04 | $40.00 |
BB135 Overview
A varactor diode (also called a variable capacitance diode, varicap, or tuning diode) is a semiconductor device operated under reverse bias whose junction capacitance varies predictably with the applied voltage. In the broader component hierarchy, it belongs to the diode family within discrete semiconductors, and it serves as the fundamental tuning element in voltage-controlled oscillators, RF filters, and electronically tuned resonant circuits. Instead of a mechanically variable capacitor, designers use a varactor plus a control voltage to sweep a resonant frequency.
Key features of the BB135 include excellent capacitance-voltage linearity, which simplifies linear frequency tuning over wide ranges; a very small plastic SMD SOD-323 package that minimizes parasitic inductance and saves board area in dense RF layouts; a low series resistance that improves Q factor in tuned circuits; and a 30 V reverse-voltage rating that provides margin on high-swing tuning nodes. The matched type BB134 offers the same specification, allowing pair usage where two closely matched tuning diodes are needed.
Technically, the BB135 uses planar junction technology, which yields tight capacitance distribution and stable behavior over temperature - critical attributes for UHF applications where picofarad-level differences directly shift the oscillation frequency. Its low capacitance makes it especially suitable for the higher end of the UHF band, where larger-capacitance varactors would excessively load the resonant tank.
Typical applications include electronic tuning in UHF television tuners, radio upconversion concepts, and VCO tuning in RF front ends. It also fits antenna matching networks and tunable filters in communication receivers.
Design consideration: keep the tuning-voltage source high-impedance and well decoupled, since any noise on the reverse bias modulates the oscillation frequency; series feed resistors of tens of kilo-ohms are typical to isolate the tank from the control loop.
This page synthesizes distributor pricing, drop-in alternatives including the matched BB134 and second-source equivalents, and practical RF design notes not consolidated in the manufacturer datasheet.
Drop-in alternatives for BB135 β 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 BB135 (same form factor and footprint) β differing in Linearity, Package, Series Resistance.
Quick Comparison Tool β Select alternative parts for side-by-side comparison:
BB134,115
β Drop-Inπ Reference alternative (not in catalog)
BB135,115
β Drop-Inβ In Stock
$0.11 / Unit
View Datasheet βBB135
β Drop-Inβ In Stock
$0.04 / Unit
View Datasheet βBB135
β Drop-Inβ In Stock
$0.04 / Unit
View Datasheet βBB132
β Drop-In β οΈ εζ°εΎ ιͺθ―π Reference alternative (not in catalog)
BB135 Maximum Ratings & Electrical Characteristics
| Device Type | UHF variable capacitance diode (varactor) |
| Configuration | Single |
| Reverse Voltage (VR) | 30 V |
| Capacitance at 28 V | 2.1 pF |
| Capacitance Ratio | 10 |
| Technology | Planar |
| Series Resistance | Low (typ. per datasheet) |
| Linearity | Excellent (capacitance-voltage linearity) |
| Application Band | UHF |
| Package | SOD-323 (SC-76) |
| Mounting Type | Surface Mount |
| Pin Count | 2 |
| Matched Type | BB134 (same specification) |
| Orderable Part Number | BB135,115 |
| Packing | Reel 11in Q1/T1 in LargePack |
| Min Package Quantity | 10000 |
| Lead Time | 99 weeks (per NXP, as of 2026-09-14) |
BB135 Pin Configuration
| Pin 1 | Cathode β Cathode terminal; band-marked side, driven by positive tuning voltage for reverse bias |
| Pin 2 | Anode β Anode terminal; connects to the RF ground side of the resonant tank |
Typical Applications
BB135 is suitable for 6 applications: UHF Television Tuner Electronic Tuning, Voltage-Controlled Oscillator (VCO), Radio Upconversion Concepts, Tunable RF Filters, Antenna Matching Networks, Frequency Modulation and Phase-Locked Loops.
UHF Television Tuner Electronic Tuning
The BB135 was originally designed for electronic tuning of UHF television tuners, and it remains a canonical fit for this role. Its low capacitance of about 2.1 pF at 28 V with a ratio of 10 lets the tank resonate across the full UHF broadcast band (roughly 470-860 MHz) while a 0-30 V tuning voltage sweeps the varactor. The excellent C-V linearity means channel tracking requires simpler correction than with less linear diodes, and the low series resistance preserves tank Q so image rejection and noise figure targets are met. In a tuner front end, the varactor typically sits across the input bandpass and local oscillator tanks, driven through high-value feed resistors from a regulated tuning rail to keep modulation noise out of the LO.
Recommended
Voltage-Controlled Oscillator (VCO)
In a UHF VCO, the BB135 forms the voltage-dependent element of the LC tank, converting a control voltage into an oscillation frequency. The diode's capacitance ratio of 10 gives a wide, roughly octave-spanning tuning range, and its low series resistance keeps the effective tank Q high enough to satisfy phase-noise requirements at UHF. Designers typically couple the varactor to the inductor through a small fixed capacitor to limit the loading range and to set the sensitivity (MHz per volt). Because any ripple on the reverse bias appears directly as FM, the control line should be filtered and derived from a low-noise reference. Compared with PN-junction varactors of higher capacitance, the BB135 minimizes parasitic loading in the gigahertz region where every tenth of a picofarad shifts the band edge.
Recommended
Radio Upconversion Concepts
NXP explicitly lists radio upconversion concepts among BB135 applications. In upconversion receivers and transmitters, tunable LC filters built with the BB135 move intermediate signals to higher frequency bands while rejecting images, and the diode's predictable C-V law lets the synthesizer and filter track together from a common tuning voltage. The planar process yields tight capacitance distribution unit to unit, which reduces the trim effort in production alignment. Because upconversion stages run at UHF and above, the 2 pF-class capacitance of the BB135 is essential - higher-capacitance varactors would load the small inductors needed at these frequencies. A bias network with a series resistor and bypass capacitor isolates the RF path from the tuning supply while establishing the reverse bias.
Recommended
Tunable RF Filters
Electronically tunable bandpass filters for receivers and test equipment use the BB135 as the variable element in LC resonators, replacing mechanically ganged capacitors. With a ratio of 10 between low-voltage and high-voltage capacitance, a single tuning line can sweep the passband across a wide fractional bandwidth, and the excellent linearity simplifies the control-law correction needed to keep the filter aligned. Low series resistance is decisive here: filter insertion loss scales directly with the resonator's equivalent series resistance, so a low-Rs varactor preserves passband flatness and stopband rejection. The SOD-323 package contributes minimal lead inductance, an advantage at UHF where a few nanohenries of parasitic series inductance would otherwise dominate the effective impedance.
Recommended
Antenna Matching Networks
Adaptive antenna matching networks - increasingly common in mobile and IoT transmitters - use varactors to tune a pi or L network so the antenna presents an optimal load to the power amplifier as the environment changes. The BB135's 30 V rating allows high RF swing on the tuning node without forward-biasing or breakdown, and its low 2 pF-class capacitance suits the very small effective reactances needed at UHF/SHF bands. Its C-V linearity yields a smooth, monotonic impedance versus control-voltage characteristic, which is what closed-loop matching algorithms need to converge reliably. Note that varactor losses (series resistance) add directly to network insertion loss, so an RF-matching design must budget the diode's Rs in its efficiency calculation and keep the control bias network high-impedance at RF.
Recommended
Frequency Modulation and Phase-Locked Loops
In PLL synthesizers and FM modulators, the BB135 acts as the loop's frequency-control element: the charge-pump output, filtered, drives the varactor to pull the VCO onto the programmed frequency. The linearity of the C-V curve yields a predictable VCO gain (Kvco), which stabilizes loop dynamics across the band; its low capacitance supports UHF oscillators that would be impractical with higher-capacitance tuning diodes. The 30 V reverse rating gives designers the option of operating at high bias, where the C-V curve flattens and sensitivity is reduced - useful for coarse range switching in multi-band loops. Proper layout keeps the tuning node shielded from digital crosstalk, since injected noise on the varactor bias converts directly into reference spurs and phase noise.
Recommended
Recommended Products Summary
Engineering reference data for BB135 β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | BB134,115 | BB135,115 | BB135 (LRC) | BB132 |
|---|---|---|---|---|---|
| Package | SOD-323 (SC-76) | SOD-323 (SC-76) - same | SOD-323 (SC-76) - same | SOD-323 (SC-76) - same | SOD-323 (SC-76) - same |
| Brand | NXP Semiconductors | NXP Semiconductors | NXP Semiconductors | Leshan Radio Company | NXP Semiconductors |
Key Differentiators
- Manufacturer-designated matched pair availability (vs BB134,115)
- Very low capacitance for UHF operation (vs BB132)
- Established multi-source availability (vs BB135 (LRC))
Design Notes
Keep the varactor loop as small as possible. In UHF tanks, the series inductance of even the SOD-323 package plus PCB traces adds to the effective impedance and shifts the tuning range downward. Place the BB135 directly across the inductor, use short, wide traces, and return the anode to a solid RF ground via with minimum inductance. Avoid routing the tuning voltage trace near clocks or switching nodes; coupling there converts digital noise into FM sidebands on the oscillator.
Bias the cathode through a high-value series resistor (typically 10k to 100k) so the tank never sees the low impedance of the tuning supply at RF, and decouple the tuning node with a capacitor sized to pass only the intended modulation bandwidth. Noise or ripple on the reverse bias modulates the junction capacitance directly - every millivolt of control-line noise becomes frequency modulation. Derive the tuning voltage from a quiet reference, not a switching rail, in phase-noise-sensitive designs.
Verify diode orientation: the SOD-323 polarity band marks the cathode, which must connect to the positive tuning voltage. A reversed BB135 is forward-biased and shorts the tank. Also, the RF swing at the varactor must stay below the reverse bias across the whole cycle; if the instantaneous voltage approaches zero, the capacitance rises sharply, producing harmonic distortion and intermodulation in the tuned circuit. Budget margin at the highest RF swing point, and confirm second-source parts against the NXP C-V curve before volume use.
Compliance Information
The provided web data does not include explicit RoHS/REACH statements for the BB135; the ,115 suffix conventionally indicates a RoHS-compliant NXP ordering code, but this must be confirmed on the NXP product page before compliance claims are made.
