GaN chip identification help - Page 1
Forum section: electronics / rf-microwave

author: suj
author_rank: Regular Contributor
timestamp: March 09, 2020, 06:27:01 pm
content: Can you help me identify the chip? This little EVB came to me today. I suppose this is produced by Qorvo (by analogy, I have another EVB Qorvo and they look very similar). From what I see it is a three stage power amplifier, comparing with similar ones probably at a frequency of about 10 GHz. Rather GaN, I suppose with 20..30 W output power.EVB is built on a fairly solid and heavy base, Southwest Microwave 2.92 mm connectors are used on the input and output (typical for Qorvo). The plate does not look like a production version, 50 Ω lines are in the form of prefabricated thin-film lines on an Al2O3substrate. The bare die dimensions are approximately 5.1 x 6.8 mm. I was looking for current and historical Qorvo, Triquint, RFMD chips and nothing fits. I definitely excluded TGA2590 (5.4 x 7.0 mm) and TGA2238 (5.49 x 7.0 mm) - I have these and they look different. Does anyone have any idea what this chip could be?

author: daqq
author_rank: Super Contributor
timestamp: March 09, 2020, 08:48:13 pm
content: No clue, but try mailing them. I succeeded in identifying an old tube, decades out of production by just asking the manufacturer.

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: March 10, 2020, 12:33:51 pm
content: That output looks strange. What I would expect is the bias line (thin, with 1-turn coil for stability) is the output, and the big fat lines are the biases.Interesting to see how different these chips look to what I'm used to.Good luck on your hunt.

author: suj
author_rank: Regular Contributor
timestamp: March 10, 2020, 01:01:54 pm
content: I think I will try to measure something. First of all, I'll make conservative bias assumptions based on similar chips. Next, I'll try to determine what band the chip is on using low signal levels. I have VNA to 50 GHz, attenuators 50 W to 18 GHz and 20 W to 40 GHz so there will be no problem. Then I will try to increase the signal (at a pre-determined frequency) observing the compression at the output. 1dB and 3 dB compression will allow me to compare the level with the chips for which this data is published in the datasheets. It would suit me best if this amplifier could work in a 3 cm amateur band. I have 2 pieces so the combined power could be significant. Of course, if it could work with CW signals, not just impulse ones. In this case maybe it would help appropriate derating.

author: suj
author_rank: Regular Contributor
timestamp: March 11, 2020, 12:57:11 am
content: I already know a little bit more. As I mentioned earlier, I have 2 pieces EVB with this mysterious chip. I prepared the measurement environment and tried to polarize the gate. Unfortunately, it is not typical for the gate current to be 100 mA at -1.5 V and drain voltage 0 V... The chip in this EVB is burned.Fortunately, the second copy of this EVB works differently. First, I set the gate polarization with a voltage -5 V, and gate current was 0 mA. Then I increased the drain voltage to +24 V with the gate blocked. I increased the gate voltage to about -2.6 V so that the drain current reaches 0.65 A. Then I gave a signal from VNA with a frequency of 4 to 18 GHz with a level of about 0 dBm at the amplifier input. Second VNA port via a set of 30 dB/50 W attenuators to amplifier output. VNA calibrated by simple response type calibration. The effect is this:- as expected, low signal gain is about 30 dB- the bandwidth of the amplifier fits my goals perfectlyTo make measurements at higher powers I need to prepare myself a bit. My generators at 10 GHz allow about +15 dBm. This is not enough to saturate this amplifier. I probably need + 25..27 dBm. Next problem is power supply. If I connect two channels of my Rigol DP832 in parallel, I get a maximum of about 6.4 A. It may not be enough, I need something bigger. And cooling. To lose 150 W from this small plate I need a perfect connection with a large heat sink.Preliminary results are not bad.

author: fourierpwn
author_rank: Regular Contributor
timestamp: October 08, 2020, 07:58:17 am
content: Interesting thread. Bumping to see if the OP has any further updates.

author: suj
author_rank: Regular Contributor
timestamp: October 08, 2020, 08:04:30 am
content: I checked a little more. I used a bias of Vd=20 V and Id=2 A, driving around 14 dBm from the generator and I got the power of 15 W. I did not measure the compression yet, because this test was to be used as a driver of a larger PA. I think the power could be even greater. The amplifier is very efficient, with an output power of 15 W, it draws approximately 43 W DC.