This is an Ultra Linear Test Amplifier from 1MHz to 200MHz with outstanding linear performance. It provides almost no harmonics and the intermodulation distortion (IMD) is so low that it is hard to measure how good it is. The amplifier provides easily very clean 10W output and more with a 50V supply. This amplifier is mostly intended for test use because it is optimized for signal purity but not for efficiency. With a 50V suplly voltage and 2.5A bias current it requires a pretty big heatsink for continuous operation.

JUMA ULTA10 revision B layout

Negligible harmonics

Negligible IMD products Mostly phase noise of the signal generators

Photo of an early prototype

Suitable heatsink width is 140mm to allow thru hole mount connectors. A cooling fan can be used in long-term use. In this photo BNC connectors are installed on the heatsink side.

Two amplifiers can be installed in parallel on 150mm long heatsink.  SMA or BNC connectors can be installed on top or to the bottom.  You can add spacer studs as seen in the photo to arrange the heatsink upward.

Features
- Negligible harmonics
- Negligible IMD products
- 50 ohm Input and output, PCB is compatible for SMA and BNC connectors
- Typical gain 25dB
- Frequency range 1MHz-200MHz
- Supply voltage 24V-50V, best performance with 50V
- Bias current adjustment and bias balance trimmer for 2f harmonic nulling
- 2.0A - 2.5A bias current for ultra linear operating point
- Temperature compensated bias current
- Output power 10W or more with 50V supply
- PCB dimesions 170mm x 74mm, FR4 thickness 1.6mm with plated holes

This test amplifier is very useful when testing a high power linear amplifier IMD behavior. See a two tone IMD measurement application note here.
If you want to use this amplifier as a "normal" 25W class AB power amplifier reduce the bias current down to 200mA for better efficiency.
 
Downloads
- Schematics (PDF)
- Layout (PDF)
- BOM (Excel)
- Measurements by OH2NLT

Update 2024-09-20 OH7SV

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