BB135,135 - 30V UHF Varactor Diode, 2.1pF | NXP Semiconductors
MPN: BB135,135 β End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $0.07 | $0.07 |
| 10 | $0.07 | $0.70 |
| 100 | $0.07 | $7.00 |
| 500 | $0.07 | $35.00 |
| 1,000 | $0.07 | $70.00 |
BB135,135 Overview
A varactor diode is a special type of diode operated in reverse bias, where the depletion-layer capacitance varies predictably with applied reverse voltage. In the broader component hierarchy, a varactor belongs to the variable-capacitance diode family within RF discrete semiconductors, and it effectively replaces a mechanically tuned variable capacitor in voltage-controlled tuning circuits.
Key features of the BB135 include excellent capacitance-voltage linearity, a capacitance ratio of approximately 10 between low and high reverse voltage, low series resistance for high Q at UHF frequencies, and a very small plastic SMD package. These characteristics make it suitable for frequency tuning where a wide tuning range and stable tracking are required.
The BB135 is fabricated in planar technology, which yields tight capacitance matching and low leakage. According to the NXP datasheet, the matched type BB134 has the same specification, and both devices target electronic tuning in UHF television tuners, radio upconversion concepts, and voltage-controlled oscillators (VCOs). The 30 V cathode rating allows tuning voltages spanning most of the useful capacitance-ratio range.
Typical applications include UHF tuner local-oscillator tuning, AFC and VCO tank tuning, and RF upconversion stages where a voltage-controlled capacitor adjusts resonant frequency. Its low capacitance (about 2 pF at high bias) suits low-frequency-to-UHF resonant tanks without excessively loading the circuit.
Design consideration: because the diode is reverse-biased at all times, keep reverse leakage low and avoid forward conduction during large RF swings by ensuring the RF voltage across the diode does not exceed the DC reverse bias at the minimum-bias point.
This page synthesizes distributor pricing, drop-in alternative guidance, and practical design notes not found in the manufacturer datasheet, giving engineers a complete selection view for this EOL varactor.
Drop-in alternatives for BB135,135 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:
BB134
β Drop-Inπ Reference alternative (not in catalog)
BB135A
β Drop-In β οΈ εζ°εΎ ιͺθ―π Reference alternative (not in catalog)
BB135,135 Maximum Ratings & Electrical Characteristics
| Device Type | UHF variable capacitance diode (varactor) |
| Reverse Voltage (VR) Max | 30 V |
| Capacitance CD @ VR = 28 V, f = 1 MHz | 2.1 pF |
| Capacitance C28 (typical) | 1.9 pF |
| Capacitance Ratio | 10 (typical) |
| Measurement Frequency | 1 MHz |
| Technology | Planar silicon |
| Package | SOD-323 (SC-76) plastic SMD |
| Mounting Type | Surface Mount |
| Matched Type | BB134 (same specification) |
| Applications | Electronic tuning in UHF TV tuners; radio upconversion; VCO |
| Packaging | Tape & Reel (Tape 13, reel 11.25 inch LargePack) |
| Minimum Package Quantity | 10000 |
| Minimum Order Quantity | 10000 |
| Lead Time | 99 weeks |
BB135,135 Pin Configuration
| Pin 1 | Cathode (K) β Cathode; connect positive tuning (reverse bias) voltage here |
| Pin 2 | Anode (A) β Anode; RF / ground reference side of the tuning circuit |
Typical Applications
BB135,135 is suitable for 6 applications: UHF Television Tuner Electronic Tuning, Voltage-Controlled Oscillators (VCO), Radio Upconversion Concepts, AFC and Frequency Correction Circuits, RF Tunable Filters, Parametric and Harmonic RF Circuits.
UHF Television Tuner Electronic Tuning
The BB135 was designed primarily for electronic tuning in UHF television tuners. Its 10:1 capacitance ratio spans the tuning range needed to cover UHF local-oscillator bands with a single tank inductor, while the 2.1 pF capacitance at 28 V limits loading of high-frequency resonators. Placed across the tuner tank with a buffered tuning voltage (0-28 V typical), it converts a DC control voltage into a resonant frequency shift. Low series resistance preserves tank Q, directly reducing local-oscillator phase noise. Designers should route the tuning node with a high-value series resistor to isolate RF from the tuning supply and avoid forward bias at minimum tuning voltage.
Recommended
Voltage-Controlled Oscillators (VCO)
In VCO tank circuits, the BB135 provides voltage-controlled capacitance from roughly 10-20 pF class at low bias down to about 2 pF at 28 V, giving a wide frequency-tuning span. Its low series resistance minimizes loaded-Q degradation, which is critical for phase noise in PLL-synthesized oscillators. The 30 V reverse rating allows the full tuning range without breakdown risk. Best practice is to connect the varactor through a DC-blocking capacitor and bias via a large-value resistor, so RF swing superimposed on the tuning voltage never forward-biases the junction - forward conduction causes harmonic distortion and tuning hysteresis. The SOD-323 package contributes minimal parasitic inductance at UHF.
Recommended
Radio Upconversion Concepts
NXP lists radio upconversion as a target application for the BB135. In upconversion architectures, the local oscillator that mixes a low intermediate frequency to RF benefits from a varactor-tuned VCO: the BB135 supplies the voltage-controlled tank capacitance with a smooth, linear C-V characteristic (a headline datasheet feature: excellent linearity). Linearity reduces tuning-law errors and simplifies AFC loop design. The 1 MHz measurement condition and 30 V rating give designers a predictable, wide-range tuning element. Typical implementation places the varactor in the LO tank with a 10:1 tuning-voltage span, and the low ~2 pF high-bias capacitance suits the high-impedance tanks of UHF LO stages.
Recommended
AFC and Frequency Correction Circuits
Automatic frequency control loops use the BB135 as a fine-tuning element that steers an oscillator back to the locked frequency. Because the varactor capacitance changes smoothly with reverse voltage, small correction voltages produce proportional frequency shifts, ideal for narrow-range AFC. The BB135 has 30 V headroom, so the AFC voltage can be summed on top of a coarse tuning voltage without approaching breakdown. Its planar construction gives repeatable, low-leakage behavior so the high-impedance AFC node holds its voltage; keep the bias network resistance in the hundreds of kilohms to avoid loading the loop filter while still draining leakage current.
Recommended
RF Tunable Filters
Voltage-tunable LC bandpass filters for receiver front-ends can use the BB135 as the variable element across a coupled-resonator design. The capacitance ratio of 10 gives a wide center-frequency tuning span, while low series resistance keeps insertion loss acceptable at UHF. With about 2 pF at maximum bias, the varactor also works as a small, lightly-coupled tuning capacitor where a fixed capacitor would be too large. Designers should account for the SOD-323 parasitic inductance (~1-2 nH class) when simulating tank resonance, and bias each resonator's varactor through separate decoupled nodes to preserve filter selectivity.
Recommended
Parametric and Harmonic RF Circuits
Varactors such as the BB135 can serve in parametric multipliers and voltage-controlled phase shifters, where the nonlinear but controllable C-V characteristic is exploited deliberately. The BB135's low series resistance and high capacitance ratio improve conversion efficiency in such circuits, and its planar silicon junction offers stable, repeatable nonlinearity. In phase-shifter networks, varying the reverse bias shifts the electrical length of an LC section - the 10:1 capacitance range enables substantial phase control with only a 0-28 V drive. As the part is EOL, use these designs for legacy service or verify BB134 availability before new production.
Recommended
Recommended Products Summary
Engineering reference data for BB135,135 β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | BB134 | BB135A |
|---|---|---|---|
| Package | SOD-323 (SC-76) | SOD-323 (SC-76) - same | SOD-323 (SC-76) - same |
| Brand | NXP Semiconductors | NXP Semiconductors | NXP Semiconductors |
| Reverse Voltage | 30 V | 30 V | 30 V |
Key Differentiators
- Excellent C-V linearity (vs BB134)
- Very small SMD package for UHF (vs BB134)
- Wide capacitance ratio of 10 (vs BB135A)
Design Notes
Never allow the varactor to become forward-biased during operation. The instantaneous RF voltage across the BB135 adds to the DC tuning voltage; at minimum tuning bias, the negative RF half-cycle can forward the junction, generating harmonics, pulling the oscillator, and rectifying current that detunes the loop. Keep the RF swing at the anode comfortably below the DC reverse bias, or AC-couple the varactor and return it to a bias point of at least several volts. Also verify the SOD-323 cathode bar orientation before reflow - reversed varactors will not tune.
Place the BB135 directly across the resonator tank with the shortest possible traces; at UHF, even a few millimeters of trace adds inductance that shifts the tuned frequency. Connect the tuning-voltage node through a 10-100 kilo-ohm series resistor located close to the varactor to isolate RF from the tuning supply and to keep the tank Q high. Decouple the bias node with a capacitor to ground at RF frequencies. Keep the SOD-323 footprint pad dimensions to the datasheet land pattern to minimize parasitic capacitance between anode and cathode pads.
The BB135 is a reverse-biased tuning element and dissipates negligible DC power, so thermal design is not a concern. The main reliability variable is reverse voltage: respect the 30 V maximum rating including transients on the tuning line. Tuning supplies derived from boosted rails should be clamped. Because the part is EOL at NXP (page shows End of Life overview, last listed lead time 99 weeks), qualify the matched BB134 or a second-source SOD-323 UHF varactor now if this device remains in long-term production bills of material.
Compliance Information
The NXP product page includes an Environmental Quality section, but specific RoHS/REACH compliance values for BB135,135 were not present in the provided data; consult the NXP product page for current compliance declarations.
