EDNE February 2013 - (Page 16)

A mo insight intonthly T&M techn the latest o the pages logy from Measurem of Test & (www.tmw ent World orld.com ) Test & Measurement World is the leading monthly magazine for engineers and managers in the electronics testing industry. ® An economy low-noise instrumentation preamp Using a pre-amp ahead of a measurement instrument such as a spectrum analyzer, when low-level signals are being explored, can lower noise floor and reveal more signal detail. The evaluation platform for a new wideband amplifier IC offers a low-cost option. ® Kenneth Wyatt, in Test & Measurement World’s “EMC blog” L ast year Mini-Circuits developed a (really!) low-noise, broad band, preamp (model PSA4-5043+) for use as a front-end amplifier for mobile telecom applications, such as GSM, CDMA, LTE and WiMax. However, it would also be ideal to act as a pre-amplifier for spectrum analyzers: the low-noise feature would lower the effective noise figure of the analyzer, allowing you to see low-level signals better. This would not only be useful for amplifying near-field or current probe outputs, but would work well to boost the antenna output in semi-anechoic chambers - especially if there is a long run of coax cable. The PSA4-5043 costs about $2.50 in quantities of 20; however, rather than ordering the device itself, note that Mini-Circuits sells the amplifier already built into a high-quality test board and brass housing (model # TB-653+) for just $59.95 in single quantities. It’s orderable right off their web site. The MMIC amplifier is based on E-PHEMT technology and is specified from 50 MHz to 4 GHz with an amazing noise figure of 0.73 to 1.44 within that frequency range. The output power at 1dB compression is about 16 to 20 dB and the third-order intercept ranges from 28 to 31 dB. It should operate moderately well in high dynamic range environments. It’s really quite good for a single four-legged SOT-343 device. In addition, it’s also rated Class 1B (HBM) at 500 to <1000V for ESD. I tried measuring the preamp using my Rigol DSA815TG spectrum analyzer (with tracking generator) and found the gain to vary from 25 to 15 dB from 1 to 1,500 MHz (the upper limit of the analyzer), just as the data sheet specifies. Note that, despite Mini-Circuit’s spec of 50 MHz for the lower limit, I found it would amplify all the way down to 5 MHz. To power the preamp, I took a spare USB cable and cut off the larger end, leaving enough to reach the USB port on the analyzer. On my cable, the +5V was the red wire, and black was the return. Be sure to verify your cable using a volt meter before connecting to the preamp. I adjusted the tracking generator output to -20 dBm, so the preamp wouldn’t saturate. I also changed the vertical scale from 10 dB to 5 dB per division, so I could observe gain changes more easily. After normalizing the analyzer, I adjusted the offset so the positive gain would display properly on the screen. You’ll want to print out this gain versus frequency plot (or save as a calibration table) in order to Figure 1. The gain of the preamp from 1 to 1,500 MHz (the limit of the analyzer). provide a calibration factor for It varies from 25 to 15 dB as per the Mini-Circuits data sheet. certification testing or for accu- 16 EDN EUROPE | February 2013 www.edn-europe.com http://www.tmworld.com http://www.edn-europe.com

Table of Contents for the Digital Edition of EDNE February 2013

RS Components
Agilent Technologies
Maxim Integrated
Signal Integrity
Mesago SMT 2013
Test & Measurement World
Rohde & Schwarz
Mesago PCIM 2013
Mechatronics in Design
Hot technologies: trends to watch in 2013
Hot 100 products of 2012
Add LED intelligence to improve light quality, efficiency, and cost
Design Ideas
Product roundup
Tales from the Cube

EDNE February 2013