Oscilloscope Preamplifier LNA10
$385.00
Most oscilloscopes can’t resolve signals below about 1 mV. The LNA10 low-noise differential preamplifier brings that down to sub-microvolt levels, with 4 nV/√Hz input noise and a tunable 1 Hz–1 MHz low-pass filter.
Description
The LNA10 Low-Noise Oscilloscope Preamplifier lets you see sub-microvolt signals on a standard oscilloscope. Most scopes bottom out at 1 mV/div, which is far too coarse for small, low-frequency signals. The LNA10 amplifies the signal with very little added noise and filters out the bandwidth you don’t need.
Key features
- True differential analog input
- Analog low-pass filter, tunable from 1 Hz to 1 MHz
- Input-referred noise of 4 nV/√Hz or less above 100 Hz
- Lower noise than typical solid-state amplifiers at every frequency (see the Noise Characteristics table under Specifications)
What that means in practice: at 1000× gain with a low-impedance source, total noise from 100 Hz to 1 kHz stays under one division peak-to-peak at 1 mV/div.
Why small, low-frequency signals need a dedicated preamp
Oscilloscopes are built for fast events, where a millivolt or more of noise is normal. Slow signals are different. They carry much less intrinsic noise, so a scope’s own noise floor can bury them completely. To see them you need two things: a low-noise preamp to lift the signal above the scope’s noise, and a filter to limit bandwidth to the range you care about.
Amplifier noise adds a complication. Above roughly 1 kHz, most solid-state amplifiers have a flat (“white”) noise spectrum, specified in nV/√Hz. At lower frequencies the noise rises, and below about 10 Hz it rises steeply. This is called 1/f or flicker noise, and resistors don’t show it the way semiconductors do. The LNA10 is designed to keep noise low across the whole range, including the low-frequency region where ordinary amplifiers struggle.
A note on thermal noise
Every resistive source generates thermal (Johnson) noise proportional to √(R·Δf), the square root of source resistance times bandwidth. For example, a 1 kΩ resistor produces about 13 nV RMS in any 10 Hz bandwidth, whether that’s 0–10 Hz or 102–112 Hz. If you quadruple either the resistance or the bandwidth, the noise doubles. Low source resistance and a narrow bandwidth mean low noise, which is why the LNA10’s adjustable filter matters.
Specifications
| Gain | Selectable 10x/100x/1000x (true differential, with CMRR > 90dB) Positive and negative single-ended inputs can be selected, as well as reference ground (LNA10 does not have 1x gain) |
| Gain Accuracy | +/-1% |
| Output Filter | Single Pole Low Pass, tunable from 1Hz to 1Mhz (used to reduce bandwidth, as needed) |
| Input Signal Coupling | Selectable AC or DC AC passes through a .3Hz High Pass filter, 1 pole. When AC coupled, an offset as much as +/-30V can be tolerated at the input. In this case, if the inputs rapidly vary by more than .8V peak-to-peak, then the slew rate must be ≤ 2V/sec for accurate amplification. DC, each input must be between -0.4V and +0.4V, with respect to case ground, for accurate readings. |
| Input Offset Adjustment | +/- 1 mV |
| Input Protection | +/- 5KV ESD (static). +/-30V unlimited current transients, with respect to case ground. |
| Input Impedance | 1MΩ |
| Input type | BNC |
| Output Impedance | 470Ω |
| Output Type | BNC (100Ω) The output is designed to be connected to a single oscilloscope channel, or any other voltage-reading device (data logger, voltmeter, etc). |
| Input Power | 12VDC (~50mA min) |
Noise Characteristics
| 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.