BAP51-05W - Dual PIN Diode 50V SC-70 | NXP Semiconductors
MPN: BAP51-05W β Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $0.28 | $0.28 |
| 10 | $0.22 | $2.20 |
| 100 | $0.15 | $15.00 |
| 500 | $0.11 | $55.00 |
| 1,000 | $0.09 | $90.00 |
BAP51-05W Overview
A PIN diode (positive-intrinsic-negative) is a special type of diode with a wide, lightly doped intrinsic region between the P and N layers. This intrinsic layer makes the PIN diode behave as a nearly ideal, current-controlled RF resistance when forward biased and as a low-capacitance, high-blocking element when reverse biased. Within the power-management and signal-chain hierarchy, PIN diodes belong to the RF diode family alongside varactors and Schottky diodes, and they are the standard switching element in RF front ends, attenuators, and antenna switching networks.
Key features of the BAP51-05W include low diode capacitance for minimal loading of RF signal paths, low forward resistance (RF series resistance) for low insertion loss in the on-state, two matched diode elements in one package for balanced series/shunt attenuator topologies, and automotive-grade AEC-Q101 qualification. The small SC-70 footprint (2.0 x 1.25 mm body) conserves board area in dense RF modules.
Architecturally, the common-cathode pair allows the device to serve as a series-connection element in voltage-variable attenuators, where one diode can be placed in the signal path and the second in a shunt or reference leg, simplifying bias networks and improving thermal tracking between elements. Because both dice share the same package thermal environment, resistance matching over temperature is superior to two discrete diodes.
Typical applications include RF switching circuits in transceivers, voltage-variable attenuators in cellular and wireless infrastructure, AGC (automatic gain control) circuits, and antenna switch modules in automotive and industrial radio systems. The 50 V reverse rating also provides margin in higher-voltage bias designs.
Design consideration: PIN diode RF resistance is proportional to forward bias current, so bias network stability directly determines attenuation accuracy; use a temperature-stable current source and adequate RF bypassing of the bias feed.
This page synthesizes distributor pricing, drop-in alternatives, design notes, and application guidance not found in the manufacturer datasheet.
Drop-in alternatives for BAP51-05W 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:
BAP51-02W
β Drop-In β οΈ εζ°εΎ ιͺθ―π Reference alternative (not in catalog)
BAP51-05W Maximum Ratings & Electrical Characteristics
| Device Type | General purpose silicon PIN diode (dual, common cathode) |
| Configuration | 1 pair, series connection (common cathode) |
| Reverse Voltage (VRRM) | 50 V |
| Forward Current (IF) | 50 mA |
| Total Power Dissipation (Ptot) | 240 mW |
| Package | SC-70 (SOT323), 3-pin |
| Mounting Type | Surface Mount |
| Qualification | AEC-Q101 (automotive) |
| Category Classification | RF Diode - PIN diode |
| Package Body Size | 2.0 x 1.25 mm (SC-70) |
| Number of Elements | 2 |
| Ordering Suffix | BAP51-05W,115 (tape and reel) |
BAP51-05W Pin Configuration
| Pin 1 | Anode 1 β Anode of PIN diode element 1 (series-connected pair) |
| Pin 2 | Common Cathode β Common cathode of both PIN diode elements |
| Pin 3 | Anode 2 β Anode of PIN diode element 2 (series-connected pair) |
Typical Applications
BAP51-05W is suitable for 6 applications: RF Switching Circuits, Voltage-Variable RF Attenuators, Automatic Gain Control (AGC) Circuits, Antenna Switch Modules, Automotive RF Systems, Test and Measurement RF Signal Paths.
RF Switching Circuits
In series/shunt RF switch topologies, the BAP51-05W's low diode capacitance minimizes off-state insertion loss, while its low forward resistance keeps on-state loss small at bias currents commonly in the 5-20 mA range. The dual common-cathode configuration supplies both the series element and the shunt element from one SC-70 package, halving component count and ensuring matched RF resistance because both dice share the same thermal environment. With a 50 V reverse rating, the switch tolerates large RF voltage swings and elevated bias rails. Designers should route the common cathode (pin 2) to a low-inductance RF ground and bypass the bias feed so control circuitry does not load the signal path. Per the NXP product page, this device was designed specifically for such RF switching roles in wireless transceivers and infrastructure equipment.
Recommended
Voltage-Variable RF Attenuators
PIN diode Pi- and T-attenuators rely on the proportionality between forward bias current and RF series resistance, and the BAP51-05W provides two matched, thermally coupled diodes that make this proportionality repeatable across the attenuation range. Because both dice sit in the same SC-70 body, their junction temperatures track closely, so resistance mismatch drift that would otherwise distort attenuation accuracy is largely eliminated. The 50 mA forward current rating supports the higher bias levels needed for low-resistance, low-insertion-loss states, while the 50 V blocking rating withstands peak RF voltages at minimum attenuation. A temperature-stable current source driving the common cathode yields an AGC- or digitally-controlled attenuator stage suitable for cellular bands and IF chains with 240 mW dissipation headroom.
Recommended
Automatic Gain Control (AGC) Circuits
In receiver AGC loops, the BAP51-05W acts as a voltage-variable resistance whose value is set by a control current derived from the AGC detector, providing smooth, low-distortion gain adjustment over a wide dynamic range. The low diode capacitance keeps the controlled node broadband, while low forward resistance allows deep attenuation states. AEC-Q101 qualification means the same AGC stage can be reused in automotive radio and telematics receivers without requalification of the PIN element. Because the two internal diodes share a common cathode, a single control line can steer attenuation in balanced configurations, simplifying the control loop. Designers should verify the resistance-versus-current curve from the NXP datasheet against the loop's control voltage range to guarantee monotonic gain control over temperature.
Recommended
Antenna Switch Modules
Antenna switching between transmit and receive paths in RF front ends demands a device with low off-state capacitance (to avoid desensitizing the receiver), low on-state resistance (to preserve transmit efficiency), and high breakdown voltage (to survive large transmit RF swings). The BAP51-05W addresses all three: low diode capacitance, low forward resistance at moderate bias, and 50 V blocking. Its dual common-cathode pair naturally implements a single-pole dual-throw arrangement with a shared control node on pin 2. AEC-Q101 qualification extends this topology to automotive antenna modules such as keyless-entry and shark-fin radio systems. Layout should keep the RF trace lengths short and place the SC-70 directly at the antenna feed junction to minimize parasitic mismatch.
Recommended
Automotive RF Systems
The AEC-Q101 qualification of the BAP51-05W makes it a natural choice for automotive RF subsystems, including tire-pressure-monitor receivers, keyless entry, car radio tuners, and telematics units operating in harsh thermal and vibration environments. The SC-70 package survives standard automotive SMT reflow profiles and board-flex conditions, while the 50 V reverse rating provides margin against transient conditions on the RF front end. Dual matched dice in one package reduce sourcing complexity - one placement operation instead of two - which matters on high-volume automotive assembly lines. When used here, bias circuits should be qualified over the full automotive temperature range, and PIN diode RF resistance should be characterized at the cold and hot corners to ensure the AGC or switch performance stays within specification.
Recommended
Test and Measurement RF Signal Paths
Signal generators, spectrum analyzer front ends, and network analyzer test sets use PIN diode switches and stepped attenuators for level control, and the BAP51-05W's combination of low capacitance, low forward resistance, and 50 V blocking suits these broadband, level-sensitive paths. The common-cathode pair supports compact series-shunt switch cells with well-matched resistance over temperature, improving amplitude flatness across the frequency span. In instrumentation, the 240 mW dissipation rating must be respected at high bias and high RF drive; a short thermal relief on the SC-70 pads is usually sufficient. Because instrumentation designs often demand tight amplitude repeatability, calibrating the resistance-versus-current curve per unit compensates for the few-percent device spread inherent in PIN diode processes.
Recommended
Recommended Products Summary
Engineering reference data for BAP51-05W β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | BAP51-02W |
|---|---|---|
| Package | SC-70 (SOT323), 3-pin | SC-70 (SOT323), 3-pin - same |
| Brand | NXP Semiconductors | NXP Semiconductors - same |
| Configuration | Dual PIN diode, series connection, common cathode | Dual PIN diode, common cathode |
| Primary Application | RF switching and attenuator circuits | RF switching (lower voltage grade) |
Key Differentiators
- Dual matched dice in one SC-70 package (vs Single SC-70 PIN diodes)
- Automotive AEC-Q101 qualification (vs Generic commercial PIN diodes in SC-70)
- Higher voltage grade in the BAP51 family (vs BAP51-02W)
Design Notes
Bias the BAP51-05W with a temperature-stable current source, not a fixed voltage: PIN diode RF series resistance is set by forward current, so bias drift translates directly into attenuation or insertion-loss drift. Keep average forward current within the 50 mA rating and total dissipation (diode forward voltage times current plus RF dissipation) within 240 mW. Estimated: at a typical 0.9 V forward voltage and 20 mA bias, each element dissipates about 18 mW, well within the 240 mW package limit, but verify with the actual datasheet Vf curve at your bias point.
Place the SC-70 package so that RF traces to pins 1 and 3 are short and impedance-controlled (50 ohm microstrip or CPW). Tie the common cathode on pin 2 to a low-inductance ground or bias-return node. Decouple the bias feed with an RF choke or high-value resistor plus shunt bypass capacitors rated well above the operating frequency so the control network presents an open circuit at RF and does not load the signal path.
Do not assume the pinout of other PIN diode parts matches the BAP51-05W; SC-70 PIN diodes from different vendors may place the common terminal on pin 1 or 3. Also note the voltage-specification discrepancy between distributor data (50 V) and the NXP product page description (blocking voltage to 35 V in application context): always design to the datasheet derating curve, not marketing text. Finally, do not substitute a single-diode SC-70 part for this dual common-cathode device without rewiring the pad assignment.
Compliance Information
AEC-Q101 (automotive qualification for discrete semiconductors) confirmed via datasheets.com part data. RoHS/REACH/lead-free status not stated in the provided web data and must be confirmed from the NXP product page or distributor compliance documents.
