Oscilloscope Preamplifier LNA10


 The LNA 10 oscilloscope preamp will significantly improve the small-signal performance of oscilloscopes at frequencies below 1MHz.  

SKU: LNA10 Categories: ,


Product Description: With this preamp, sub-microvolt signals can be displayed on scopes which typically only go down to 1mV/div on the vertical axis.  The preamp includes an analog true differential input and an analog low-pass filter (tunable 1Hz-1MHz).  Input-referenced RMS noise spectrum for f >100Hz is 4 nV/√Hz or less, so for example, even with 1000 x gain, total noise from 100 Hz to 1000 Hz is less than 1 div peak-to-peak on a 1mV/div vertical scope setting (assuming a low-impedance input).  Most oscilloscopes are designed to display high-frequency (fast) events that may intrinsically have noise of a millivolt or more.  However, low-frequency signals have much less intrinsic noise, so a low-noise preamp and a bandwidth-limiting filter are essential for small signals at low frequency.* Most amplifiers have a white noise spectrum (a flat spectral curve) at all frequencies above ~1000 Hz.  This white noise spectrum is usually specified as a certain number of nV per √Hz.  However, unlike typical passive resistors, the equivalent input noise spectrum of solid-state amplifiers (in nV/√Hz) becomes higher at low frequencies.  Typically the number of nV/√Hz is proportional to ~1/f for f10Hz. The table below shows actual noise of the LNA 10 in various frequency ranges. At all frequencies, the LNA 10 has much less noise than typical solid-state amplifiers.

Frequency Range: Input-referenced Noise:
10-4 – 10-2 Hz (freq range: inverse of 2.8hrs to inverse of 100sec) 50 nV RMS
10-2 Hz – 1 Hz (freq range: inverse of 100sec to inverse of 1 sec) 20 nV RMS
1 – 10 Hz 18 nV RMS (6nV/√Hz average)
10 – 100 Hz 39 nV RMS (4.1nV/√Hz)
Above 100 Hz < 4 NV/√Hz

*The intrinsic “white” noise of a resistive electrical circuit at room temperature is proportional to (R∙Δf), which is the square root of the product of source resistance multiplied by the bandwidth being investigated.  For low source resistance and low frequencies, noise is low.  For example, a 1000 Ω resistor will have an intrinsic RMS noise of 13 nV in a Δf =10 Hz bandwidth, with 10 Hz being the bandwidth, for example, associated with the frequency range 0-10 Hz,  or with the frequency range 102 Hz-112 Hz.  The noise will become twice as much if the bandwidth being studied is 4 times as wide (i.e., 40 Hz), or if the resistance is multiplied by 4. Features

  • Output has a single pole lowpass filter, tunable from 1 Hz to 1 MHz. This feature reduces the bandwidth, as needed.
  • Selectable DC/AC coupled input (“AC” passes through a .3Hz highpass filter, 1 pole): On DC, each input must be between -0.4V and +0.4V, with respect to case ground, for accurate readings. When set to AC, a DC offset up to +/- 30V can be present. (However, if the inputs rapidly vary by more than .8V peak-to-peak, then the slew rate must be ≤ 2V/sec for accurate amplification.)
  • Inputs are protected to +/- 5KV static and +/-30V unlimited current transients, with respect to case ground.
  • Output impedance is 470 Ω.
  • Selectable gains are 10x, 100x, 1000x (true differential, with CMRR > 90dB). Also positive and negative single-ended inputs can be selected, as well as reference ground. Gain accuracy: +/-1%. (The LNA 10 does not include a 1x gain.)
  • An offset adjustment, equivalent to +/- 1 mV at the input, is present.
  • A BNC output (100 Ω) is intended to be connected to a single oscilloscope channel, or to another voltage-reading device (data logger, voltmeter, etc).


LNA10 Video Demonstration

Additional information


Electrical Engineering, Scientific Research


Voltage Measurement