Analog Devices Inc. 116092-HMC475ST89

Overview

HMC475ST89 from Analog Devices (formerly Hittite Microwave) is an InGaP HBT gain block MMIC amplifier operating from DC to 4.5 GHz, delivering 21.5 dB small-signal gain, +22 dBm P1dB output power, and +35 dBm OIP3 at 850 MHz with 110 mA supply current at +8 V. It serves as a cascadable 50 Ω RF/IF gain stage or LO/PA driver in wireless infrastructure.

For engineers reviewing the HMC475ST89 datasheet, HMC475ST89 pinout, HMC475ST89 application, or HMC475ST89 equivalent, key selection criteria include its SOT89 package compatibility, broadband DC–4.5 GHz operation, single-supply biasing (8–12 V), temperature-stable Darlington topology, and verified performance in cellular, WLAN, and microwave radio signal chains.

Technical Context

The HMC475ST89 employs a Darlington-configured InGaP HBT process, enabling high gain stability over temperature (0.008–0.012 dB/°C) and reduced sensitivity to process variation. Its 50 Ω input/output impedance supports direct cascading without external matching networks across DC–4.5 GHz.

Bias is applied via Pin 3 (RFOUT/Vcc), with external R_Bias (e.g., 9.1 Ω at 8 V) setting I_CQ = 110 mA. DC blocking capacitors are required on Pins 1 (IN) and 3 (OUT); Pins 2 and 4 plus package bottom must be soldered to RF ground per RF layout best practices.

Key Specifications

Pinout & Package

Package: Industry-standard SOT89 (3-lead variant with exposed thermal pad; Pin 2 and Pin 4 are GND; package bottom must be soldered to RF ground). Dimensions per JEDEC TO-243AA outline.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar RF gain block applications.

Compared with HMC475ST89, HMC476ST89 trades 3 dB OIP3 for 1.5 dB extra gain and identical form factor, while QPL9057 provides broader bandwidth and active bias at the expense of SOT89 compatibility and added design effort.

Availability

HMC475ST89 is available at Aetrix Electronics and suitable for cellular infrastructure, fixed wireless access, and microwave radio applications requiring stable component supply, long-lifecycle support, and traceable sourcing.

Supply support for HMC475ST89 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Analog Devices acquired Hittite Microwave in 2014 and integrates its high-frequency RF portfolio into precision analog and RF solutions for communications and instrumentation.

The HMC475ST89 belongs to Hittite's legacy GaAs/InGaP MMIC gain block family, designed specifically for broadband RF/IF amplification in wireless infrastructure and test equipment where cascadability, linearity, and thermal stability are essential.

FAQ

What is the recommended supply voltage range for stable operation of the HMC475ST89?

The HMC475ST89 operates reliably with a single positive supply between +8 V and +12 V. At +8 V with a 9.1 Ω bias resistor, it draws 110 mA and delivers optimal gain and linearity. Higher voltages increase output power but require proportionally larger R_Bias values (e.g., 43 Ω at +12 V) to maintain 110 mA I_CQ. Exceeding +12 V risks violating absolute maximum ratings.

Does the HMC475ST89 require external DC blocking capacitors, and where are they placed?

Yes, the HMC475ST89 requires external DC blocking capacitors on both RF input (Pin 1) and RF output (Pin 3). These capacitors prevent DC coupling between stages while preserving 50 Ω RF impedance. Typical values range from 100 pF at 2.4 GHz to 0.01 μF at 50 MHz, selected per application frequency per the recommended component table in the datasheet.

How does the Darlington topology in the HMC475ST89 improve thermal stability compared to standard HBT amplifiers?

The Darlington configuration in the HMC475ST89 reduces gain variation over temperature to just 0.008–0.012 dB/°C across DC–4.5 GHz. This is achieved by internal current mirroring that compensates for transistor β drift, resulting in ±0.5 dB gain shift from –40°C to +85°C-significantly tighter than typical single-HBT gain blocks.

Can the HMC475ST89 be used as a direct replacement for the HMC475ST89E in RoHS-compliant designs?

No-the HMC475ST89 uses Sn/Pb lead finish and MSL1 reflow profile (235°C peak), while the HMC475ST89E is RoHS-compliant with 100% matte tin and 260°C reflow tolerance. They share identical electrical specs and pinout, but substitution requires verifying solder process compatibility and regulatory compliance for the target assembly.

What is the role of the package bottom and Pins 2 and 4 in the HMC475ST89 thermal and RF performance?

Pins 2 and 4 plus the exposed package bottom serve as primary RF and thermal ground paths. All three must be soldered directly to a solid PCB ground plane with ≥6 thermal vias to achieve specified 59.3 °C/W thermal resistance and maintain >25 dB reverse isolation. Inadequate grounding degrades gain flatness, increases noise figure, and risks thermal runaway at full power.