LA22 Lab Amplifier

Oscilloscopes and spectrum analyzers are wonderful devices—with a bit of ingenuity, you can use them to make instant graphs of nearly anything, in the time or frequency domain.  They do have a few flaws, however.  For low-level measurements, their main problem is that they're noisy; your average spectrum analyzer's noise figure is about 30 dB, and the average scope isn't much better; its most sensitive scale is usually 1 mV/div, and there's a noticeable amount of noise on the baseline.  That means that a lot of stuff that we need to see gets buried in the instrument noise.

The LA22 Low Noise Lab Amplifier makes it easy to do low-level measurements using ordinary lab equipment such as oscilloscopes, spectrum analyzers, and data acquisition bricks, whose noise levels are typically in the tens of nanovolts per root hertz.

The LA22 has 1.1-nV/√Hz voltage noise, wide bandwidth, FET input, 100× (40 dB) gain, and good manners: in the time domain, 20-ns edges with low overshoot; and in the frequency domain, 500 Hz–20 MHz bandwidth with a smooth rolloff and no high-frequency peaking.

We use them in product development, together with our NF-series active filter modules and an HP 3400A or 3403 wideband true-RMS voltmeter.  That setup makes it super easy to do final tweaking of low-noise photoreceivers and other modules: the meter reads the integrated noise in a known bandwidth with a known gain.  That way, a calibrated measurement takes only a second or two, so adjustments are fast and precise. If you don't have one of those nice meters, a digital scope that does true-RMS calculations is fine. (A regular true-RMS DMM is not fine—almost all are way too slow for this job.)

Applications

• Characterization of low noise systems
• Decrease loading on high impedance systems
• Optimizing input to digitizer
• General laboratory use
• Proof of concept & test systems

 Ordering

For larger quantities or OEM inquiries please email us at info@hobbs-eo.com.