BB135,115 - 30V UHF Varactor Diode SOD-323 | NXP Semiconductors
MPN: BB135,115 β Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $0.2 | $0.20 |
| 10 | $0.18 | $1.80 |
| 100 | $0.15 | $15.00 |
| 500 | $0.12 | $60.00 |
| 1,000 | $0.11 | $110.00 |
BB135,115 Overview
A varactor diode, also called a variable capacitance diode or varicap, is a semiconductor device operated in reverse bias that exploits the voltage-dependent depletion-layer capacitance of a PN junction. In the hierarchy of discrete semiconductors, it belongs to the diode family alongside rectifiers, Zeners, and switching diodes, but serves as a voltage-controlled passive element rather than a rectifier. Varactors are the core tuning element of LC voltage-controlled oscillators (VCOs), RF filters, and antenna tuning networks.
Key features of the BB135 include excellent capacitance-voltage linearity for predictable tuning slopes, a very small plastic SMD footprint that minimizes parasitic inductance in UHF circuits, and low series resistance, which preserves oscillator Q and phase noise performance. The 30 V repetitive peak reverse voltage (VRRM) provides generous tuning-voltage headroom above the typical 0-28 V tuner rails.
Technically, the BB135 is built on NXP planar junction technology with a hyperabrupt doping profile, delivering the high capacitance ratio of 10 between low and high reverse bias. The low series resistance directly reduces equivalent series resistance (ESR) in the resonant tank, supporting low phase-noise VCO design. Forward current capability is 20 mA average, and the device operates from -55C to +125C.
Typical applications include electronic tuning in UHF television tuners, radio up-conversion concepts, and VCO tuning in RF front ends, where the low parasitics of the SOD-323 package and smooth capacitance slope are essential.
Design consideration: keep series tuning resistors low and verify the maximum tuning voltage stays below the 30 V VRRM rating with margin; leakage current at high temperature should be checked against oscillator pulling.
This page synthesizes distributor pricing, drop-in alternatives, and practical design notes not found in the manufacturer datasheet.
Drop-in alternatives for BB135,115 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 BB135,115 (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
β Drop-Inβ In Stock
$0.04 / Unit
View Datasheet βBB135,115
β Drop-Inβ In Stock
$0.11 / Unit
View Datasheet βSMV1255-011LF
β Drop-Inπ Reference alternative (not in catalog)
BB135,115 Maximum Ratings & Electrical Characteristics
| Device Type | UHF variable capacitance diode (varactor) |
| Repetitive Peak Reverse Voltage (VRRM) | 30 V |
| Capacitance C28 (at 28 V bias) | 1.9 pF |
| Capacitance Ratio | 10 |
| Capacitance Cd, Max | 21 pF |
| Capacitance at low bias (Mouser listing) | 2.1 pF |
| Forward Current (If AV) | 20 mA |
| Series Resistance | Low (per datasheet features) |
| Operating Temperature Range | -55C to +125C |
| Package | SOD-323 (SC-76) 2-pin SMD |
| Mounting Type | Surface Mount |
| Technology | Planar |
| Linearity | Excellent (per datasheet) |
| Packing (NXP) | Reel, Min. Package Quantity 10000 (LargePack) |
| Matched Type | BB134 (same specification) |
BB135,115 Pin Configuration
| Pin 1 | Cathode β Cathode terminal; tuning (reverse bias) voltage is applied here |
| Pin 2 | Anode β Anode terminal; connected to RF/ground side of the tank |
Typical Applications
BB135,115 is suitable for 6 applications: UHF Television Tuner Electronic Tuning, VCO Tuning in RF Oscillators, Voltage-Controlled RF Filters, Antenna Tuning and Matching Networks, Radio Up-Conversion Concepts, Frequency Modulation and Phase-Locked Loop Loops.
UHF Television Tuner Electronic Tuning
Electronic tuning of UHF television tuner input and oscillator tank circuits is the primary application for the BB135,115. The device's excellent capacitance-voltage linearity provides a predictable tuning slope across the UHF band, so channel-selection DAC codes map linearly to frequency. Its 1.9 pF C28 capacitance and ratio of 10 span the tuning range needed from low-band to high-band UHF frequencies, while the 30 V VRRM rating accommodates 0-28 V tuner rails with margin. The SOD-323 package's very low lead inductance keeps parasitic resonances above the operating band, and the low series resistance preserves tank Q for clean channel selection and image rejection. Place the varactor directly across the tank inductor with a DC-blocking capacitor and high-value bias resistor to isolate the tuning supply from RF.
Recommended
VCO Tuning in RF Oscillators
The BB135,115 serves as the frequency-control element in LC voltage-controlled oscillators from VHF through UHF. Its low series resistance is the key parameter here: it directly lowers the equivalent series resistance of the resonant tank, which raises loaded Q and reduces phase noise - the dominant figure of merit for oscillator signal purity. The capacitance ratio of 10 yields roughly a 3x frequency tuning ratio in an LC tank, sufficient to cover multi-band radio up-conversion concepts cited in the NXP datasheet. Designers should bias the varactor through a large-value resistor (typically 10-47 kohm) to avoid loading the tank, and keep the tuning rail free of noise since supply ripple frequency-modulates the oscillator. Ensure the maximum instantaneous RF swing plus DC bias never exceeds the 30 V reverse rating.
Recommended
Voltage-Controlled RF Filters
Tunable band-pass and notch filters for receiver front ends use the BB135,115 as a voltage-controlled capacitor in the resonant branches. The 1.9 pF low-bias end suits high-frequency (VHF/UHF) tanks where small capacitance values and low self-resonance are required, and the ratio of 10 allows a wide center-frequency tuning span with a single control voltage. Because filter passband shape depends strongly on consistent C-V behavior across production units, the BB135's excellent linearity and matched BB134 companion simplify multi-section filter alignment. The SOD-323 package minimizes stray inductance that would otherwise distort the stopband at UHF frequencies. A common practice is to parallel two varactors to double capacitance while halving effective series resistance, improving filter insertion loss at the cost of tuning voltage scaling.
Recommended
Antenna Tuning and Matching Networks
In adaptive antenna matching networks, the BB135,115 provides voltage-controlled capacitance to retune the match as the antenna environment changes - a requirement in handheld and multi-band radio equipment. Its small SOD-323 footprint fits directly into compact matching-network PCB areas near the antenna feed point. The 30 V rating supports high-RF-swing positions in the match, though series stack arrangements should be used when the RF voltage at the feed point approaches tens of volts. The low series resistance keeps the matching network loss low, preserving transmitter efficiency and receiver sensitivity. The wide capacitance ratio enables coverage of large impedance mismatches, and the linear C-V characteristic simplifies the control algorithm mapping tuning DAC codes to match states across the -55C to +125C temperature range.
Recommended
Radio Up-Conversion Concepts
NXP's datasheet explicitly lists radio up-conversion concepts as an intended application for the BB135,115. In up-converting receiver architectures, the local oscillator and image-reject tank circuits require varactors with repeatable, low-noise tuning characteristics; the BB135's planar junction delivers both. The 1.9 pF C28 suits the high-impedance, high-Q tanks typical of up-conversion mixers operating above 100 MHz, while low series resistance prevents tank loading that would degrade conversion gain and noise figure. The device's -55C to +125C operating range supports outdoor and automotive radio platforms. Designers should characterize the complete tuning curve at the actual bias and temperature extremes, since tuning-law drift shifts the up-conversion image frequency and must be absorbed by the image-reject filter design margin.
Recommended
Frequency Modulation and Phase-Locked Loop Loops
The BB135,115 can act as the modulation element in narrowband FM generators and as the VCO tuning element inside phase-locked loop (PLL) synthesizers. Its linear capacitance slope translates directly into a predictable voltage-to-frequency gain (Kvco), which stabilizes PLL loop dynamics and simplifies loop-filter design for constant loop bandwidth across the tuning range. The low series resistance supports low phase-noise carriers needed for clean reference multiplication, and the SOD-323 parasitic floor keeps spurious resonances out of the tuning range. Because the PLL continuously sweeps the tuning voltage, verify the BB135 leakage current at 125C so that bias-resistor drops do not modulate the tuning point; a value of tens of nanoamperes is typical for planar varactors and negligible across 10-47 kohm bias resistors.
Recommended
Recommended Products Summary
Engineering reference data for BB135,115 β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | BB134,115 | BB135 (LRC) | SMV1255-011LF |
|---|---|---|---|---|
| Package | SOD-323 (SC-76) | SOD-323 (SC-76) - same | SOD-323 (SC-76) - same | SOD-323 (SC-76) - same |
| Brand | NXP Semiconductors | NXP Semiconductors | LRC (Leshan Radio) | Skyworks |
| Drop-in Replacement | - | Yes - matched type, pin-to-pin | Yes - same spec second source | Verify C-V curve first |
Key Differentiators
- High capacitance ratio of 10 for wide tuning range (vs SMV1255-011LF)
- Matched companion type for balanced designs (vs BB135 (LRC))
- Very small SOD-323 package with low parasitics (vs larger glass/SMD varactor alternatives)
Design Notes
Minimize the series inductance between the BB135,115 and the resonant tank: place the SOD-323 footprint directly across the tank inductor with the shortest possible traces. Every nanohenry of trace inductance shifts the effective capacitance and compresses the usable tuning range at UHF. The bias network should use a high-value resistor (10-47 kohm) close to the cathode so RF is isolated from the tuning supply, and the DC-blocking capacitor in series with the tank must have a self-resonant frequency well above the operating band.
Do not exceed 30 V reverse bias on the BB135,115. The instantaneous cathode voltage is the sum of the tuning DC voltage and the RF swing at the tank node, so in high-Q tanks with voltage magnification the RF peak can push the total above VRRM even with a modest tuning rail. Calculate worst-case swing at maximum drive and lowest tank impedance, and derate the tuning voltage accordingly. Also verify leakage at 125C: leakage across the bias resistor shifts the tuning point and can cause oscillator pulling in precision PLL loops.
The BB135's low series resistance is the primary contributor to tank Q; preserve it by keeping the tuning bias node clean. Noise on the tuning supply frequency-modulates the oscillator directly, so add RC or dedicated low-noise regulation (for example, an RC filter of 1 kohm and 100 nF plus 10 uF) on the tuning line. Matched pairs: when using BB135 with BB134 in balanced circuits, source both from the same reel/datasheet lot since linearity matching affects push-pull tank symmetry.
Compliance Information
Compliance status not stated in the provided web data; verify on the official NXP product page (nxp.com/part/BB135) or distributor compliance documentation before production release.
