BAP51-02 - RF PIN Diode 60V 50mA SOD-523 | NXP
MPN: BAP51-02 β Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $0.08 | $0.08 |
| 10 | $0.08 | $0.80 |
| 100 | $0.07 | $7.00 |
| 500 | $0.06 | $30.00 |
| 1,000 | $0.055 | $55.00 |
BAP51-02 Overview
A PIN diode is a semiconductor diode with a wide, lightly doped intrinsic region sandwiched between P-type and N-type regions. Under forward bias, stored charge in the intrinsic layer makes the device behave as a current-controlled RF resistor; under reverse or zero bias, it presents a small, nearly constant capacitance. This makes PIN diodes the dominant technology for RF switches, step attenuators, antenna duplexers, and AGC circuits, sitting within the broader hierarchy of diodes, discrete semiconductors, and RF components.
Key features of the BAP51-02 include its 60 V breakdown rating, which supports switching of relatively high RF swing signals, and its compact SOD-523 (SC-79) footprint of roughly 1.2 x 0.8 mm, which minimizes parasitic inductance in microwave layouts. The dual flat-lead configuration with gull-wing-free terminations supports high-volume reflow assembly. NXP characterizes the part specifically for general-purpose RF switching and attenuator service rather than rectification, distinguishing it from standard fast-recovery or signal diodes.
Architecturally, the BAP51-02 uses a silicon vertical PIN structure optimized for low series resistance (RS) when forward-biased at typical RF-switch bias currents, and low junction capacitance (CT) when reverse-biased. The ratio of these two parameters determines insertion loss and isolation in series/shunt switch topologies, which is why bias-current selection is the primary design lever.
Typical applications include antenna switching in wireless transceivers, RF attenuator stages in test equipment, transmit/receive switching in RFI-enabled devices, and protection clamping in RF front ends.
Design consideration: keep the bias resistor path high-impedance at RF (use RF chokes or large resistors) so the diode's controlled impedance is not shunted, and verify reverse bias is maintained at peak RF voltage to avoid distortion.
This page synthesizes verified distributor pricing, drop-in alternatives, comparison data, and practical design notes not found in the manufacturer datasheet.
Drop-in alternatives for BAP51-02 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:
BAP51-03
β Drop-Inπ Reference alternative (not in catalog)
BAP51-05W
β Drop-Inβ In Stock
$0.09 / Unit
View Datasheet βBAP51-02
β Drop-Inβ In Stock
$0.055 / Unit
View Datasheet βBAP51-02
β Drop-Inβ In Stock
$0.055 / Unit
View Datasheet βBAP51-02 Maximum Ratings & Electrical Characteristics
| Device Type | Silicon RF PIN Diode |
| Configuration | Single diode |
| Reverse Voltage (VR) | 60 V |
| Forward Current (IF) | 50 mA |
| Total Power Dissipation (Ptot) | 715 mW |
| Package | SOD-523 (SC-79) |
| Mounting Type | Surface Mount |
| Number of Terminals | 2 (DUAL, gull-wing-free flat leads) |
| Packing | REEL, 7 inch Q1/T1 |
| Minimum Package Quantity | 3000 |
BAP51-02 Pin Configuration
| Pin 1 | Anode β Anode terminal; forward current enters here when the diode is biased on |
| Pin 2 | Cathode β Cathode terminal; polarity band marked on package body |
Typical Applications
BAP51-02 is suitable for 6 applications: RF Antenna Switching, RF Step Attenuators, Transmit/Receive Switching in Wireless Devices, Automatic Gain Control (AGC) Circuits, RF Front-End Protection Clamping, High-Frequency Instrumentation Switching Matrices.
RF Antenna Switching
The BAP51-02's 60 V reverse voltage rating allows it to tolerate substantial RF voltage swings at the antenna port, while its low series resistance in forward bias keeps insertion loss low in the on state. In a typical single-pole throw antenna switch, the diode is placed in series with the antenna feed and biased on with a few mA through an RF choke; a shunt counterpart is reverse-biased to present low capacitance and high isolation. The SOD-523 package's small size keeps series inductance low, preserving isolation at hundreds of MHz and above.
Recommended
RF Step Attenuators
PIN diodes are the standard switching element in digitally controlled step attenuators because their RF resistance is a smooth, linear function of bias current, free from the junction nonlinearity of ordinary PN diodes. The BAP51-02's 50 mA forward current rating supports the moderate bias levels used in PI-network attenuator legs, and its 715 mW dissipation covers the power absorbed in medium-signal stages. Each SOD-523 diode occupies minimal board area, allowing dense multi-section attenuator ladders in test and measurement instruments.
Recommended
Transmit/Receive Switching in Wireless Devices
In half-duplex transceivers, the BAP51-02 can steer the antenna between the power amplifier output and the low-noise receiver input. When forward biased during transmit, its stored-charge intrinsic layer conducts RF with low distortion at moderate power levels; when reverse biased at up to 60 V during receive, its small capacitance minimizes insertion loss in the sensitive LNA path. The compact SOD-523 package suits space-constrained portable designs, and the 715 mW rating accommodates residual absorption during transmit bursts.
Recommended
Automatic Gain Control (AGC) Circuits
Because PIN diode RF resistance varies continuously with bias current, the BAP51-02 works as a voltage-controlled variable resistor in AGC and electronically controlled attenuator stages. The AGC error amplifier drives the diode bias current, smoothly scaling gain without the gain steps of switched attenuators. The diode's 60 V rating gives headroom for large signal swings, and its silicon PIN structure ensures control-line feedthrough remains low. Using the SOD-523 footprint keeps the control node compact, reducing parasitic coupling from the RF path to the AGC loop.
Recommended
RF Front-End Protection Clamping
Placed shunt to ground in an RF front end, a PIN diode such as the BAP51-02 can divert excessive RF energy during strong-signal events, protecting downstream LNAs and mixers. In normal operation the diode is effectively open (small capacitance) and contributes negligible loss; under an overvoltage condition the RF voltage self-biases the diode into conduction, clamping the node. The 60 V reverse rating and 715 mW dissipation define the survivable event energy, so designers must verify clamp energy against expected interference levels in the environment.
Recommended
High-Frequency Instrumentation Switching Matrices
Automated test and RF instrumentation matrices use arrays of PIN diodes to route signals between ports under software control. The BAP51-02's low series resistance when biased, and low, constant capacitance when unbiased, deliver consistent channel performance across a matrix, which matters for calibration repeatability. Its small SOD-523 footprint lets designers place the switching element directly at the RF connector or relay contact, minimizing stub lengths. With 60 V ratings, channels tolerate the residual swings common in multiplexed measurement systems.
Recommended
Recommended Products Summary
Engineering reference data for BAP51-02 β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | BAP51-03 | BAP51-05W | BAP51-02 (Kexin) |
|---|---|---|---|---|
| Package | SOD-523 | SOD-523 - same | SOD-523 - same | SOD-523 style - same footprint |
| Brand | NXP Semiconductors | NXP Semiconductors | NXP Semiconductors | Kexin Semiconductor |
| Device Type | Silicon RF PIN diode (single) | Silicon RF PIN diode (single) | Silicon RF PIN diode (single) | General purpose PIN diode |
| Application Focus | General purpose RF switching and attenuators | General purpose RF switching and attenuators | General purpose RF switching and attenuators | General purpose PIN diode service |
Key Differentiators
- Factory-qualified NXP silicon with full datasheet curves (vs BAP51-02 (Kexin))
- Compact SOD-523 footprint for dense RF layouts (vs Larger-package PIN diode families)
- 60 V reverse rating supports large RF swings (vs Lower-voltage small-signal switching diodes)
Design Notes
The SOD-523 land pattern is extremely small (approximately 1.2 x 0.8 mm body), so keep the RF traces directly abutting the pads and avoid long stubs, which add inductance and degrade isolation. Place the bias-feed choke or high-value resistor within a few millimeters of the anode, and use a via-to-ground immediately at the cathode for shunt configurations. Confirm cathode marking orientation against the NXP datasheet drawing before finalizing the footprint, since the SOD-523 outline is shared across many small-signal diodes.
Do not exceed the 60 V reverse rating: in RF switch circuits the reverse bias must remain greater than the peak RF voltage swing, otherwise the diode partially conducts each cycle, causing intermodulation distortion and possible parametric drift. Similarly, do not exceed the 50 mA forward current rating - higher bias lowers series resistance but this part is not rated above 50 mA; select a higher-current PIN family if your design needs it. Finally, never rely on the diode alone for DC isolation; add blocking capacitors rated for the RF swing.
The distortion performance of a PIN diode switch depends strongly on maintaining adequate reverse bias in the off state and choosing the bias current for the required on-state resistance. Estimate the off-state margin as VR_bias minus V_RF_peak and keep it comfortably positive at the maximum operating frequency and power. For low-distortion designs, derive the optimum IF bias from the RS-versus-IF curve in the official NXP BAP51-02 datasheet rather than assuming a value; typical RF-switch bias currents of a few mA are a starting point only.
Compliance Information
Compliance statuses were not stated in the provided web data; consult the NXP product page and product long-term support documentation for RoHS/REACH declarations.
