BB158

BB158 Variable Capacitance Diode Technical Summary

Overview

The BB158 is a high-performance variable capacitance diode designed for applications requiring excellent linearity and compact packaging. As a varactor diode, it provides voltage-controlled capacitance in a very small plastic SMD package, making it ideal for space-constrained designs. The BB158 offers a capacitance ratio of 15 with a nominal capacitance of 2.6pF at 28V, along with low series resistance for improved efficiency in RF circuits.

Key Features

• Excellent Linearity: Provides consistent capacitance change versus voltage characteristics for precise tuning applications
• Compact SMD Package: Very small plastic surface-mount package saves board space and enables high-density designs
• Optimized Capacitance Characteristics: C28 = 2.6 pF with a capacitance ratio of 15 delivers wide tuning range
• Low Series Resistance: Minimizes losses and improves Q-factor in resonant circuits
• RoHS Compliant: Meets environmental standards for lead-free manufacturing
• Wide Operating Voltage Range: Suitable for various biasing conditions in tuning applications

Applications

The BB158 is particularly suited for RF and microwave applications where voltage-controlled capacitance is required:

• VCOs (Voltage Controlled Oscillators): For frequency tuning in phase-locked loops and synthesizers
• RF Filters: Electronically tunable filters for communication systems
• Frequency Multipliers: Harmonic generation circuits
• Automatic Frequency Control: AFC circuits in receivers and transmitters
• Parametric Amplifiers: Low-noise amplification applications
• Tuning Circuits: AM/FM radio tuners, television tuners, and other broadcast equipment
• Phase Shifters: For beam steering in antenna arrays

Electrical Characteristics

(All measurements at T_amb = 25°C unless otherwise specified)

Absolute Maximum Ratings

• Reverse Voltage: 30V
• Forward Current: 100mA
• Power Dissipation: 150mW
• Operating Temperature Range: -55°C to +125°C
• Storage Temperature Range: -55°C to +150°C

Typical Characteristics

• Capacitance at V_R = 28V (C28): 2.6pF (typical)
• Capacitance Ratio (C1/C28): 15 (minimum)
• Series Resistance at V_R = 3V, f = 1MHz: 2.5Ω (maximum)
• Quality Factor (Q) at V_R = 3V, f = 1MHz: 100 (minimum)
• Breakdown Voltage (I_R = 10μA): 30V (minimum)
• Reverse Current at V_R = 28V: 10nA (maximum)

Capacitance vs. Voltage Characteristics

The BB158 exhibits a smooth, monotonic capacitance versus voltage curve that enables precise tuning. The capacitance decreases non-linearly with increasing reverse bias voltage, following the standard varactor diode behavior. The high capacitance ratio of 15:1 allows for wide frequency tuning ranges when used in oscillator circuits.

Package Information

Mechanical Specifications

• Package Type: SOD-323 (SC-76) plastic SMD package
• Dimensions: 1.7mm x 1.25mm x 0.95mm (L x W x H)
• Termination: Matte tin-plated leads for excellent solderability
• Weight: Approximately 3mg
• Moisture Sensitivity Level (MSL): MSL 1 (unlimited floor life at <30°C/85% RH)

Marking Information

The BB158 is marked with a single alphanumeric code on the package body for identification. The marking typically consists of "B158" or similar factory code.

Recommended PCB Land Pattern

For optimal performance and reliability, the following land pattern is recommended:

• Pad Dimensions: 0.8mm x 0.8mm (minimum)
• Pad Spacing: 1.0mm center-to-center
• Solder Paste: 0.1mm thickness recommended

Handling and Assembly Considerations

• Follow standard ESD precautions during handling and assembly
• Recommended reflow profile per JEDEC J-STD-020
• Maximum soldering temperature: 260°C for 10 seconds
• Avoid mechanical stress on the component during assembly
• Clean with isopropyl alcohol if necessary, avoiding ultrasonic cleaning

Reliability Data

• ESD Rating: HBM Class 1B (>500V)
• Moisture Resistance: Passes 85°C/85% RH testing per JESD22-A101
• Temperature Cycling: Passes 1000 cycles (-55°C to +125°C)
• Solderability: Passes JESD22-B102 solderability testing

Design Considerations

When designing with the BB158 varactor diode, consider the following:

• Use appropriate DC blocking capacitors in series with the varactor
• Implement proper RF grounding techniques for optimal performance
• Minimize stray capacitance in the circuit layout
• Use high-value bias resistors to maintain high Q-factor
• Consider temperature compensation if operating over wide temperature ranges
• For VCO applications, ensure the tuning voltage range matches the desired frequency range

Alternative Components

For applications requiring different specifications, consider these alternatives:

• BB159: Higher capacitance version (C28 = 4.5pF)
• BB154: Lower capacitance version (C28 = 1.8pF)
• BBY40: Hyperabrupt junction variant for different tuning characteristics

Environmental Compliance

• RoHS 2.0 compliant (2011/65/EU)
• Halogen-free according to IEC 61249-2-21
• REACH SVHC compliant