Amplifier
A voltage amplifier: a gain, a bandwidth set by a single pole, the noise it adds at its input, and an output limit past which it would clip.
Ports
One input, in, and one output, out.
The model
The amplifier is a single pole of gain \(G\) and bandwidth \(B\):
\[H(f) = \frac{G}{1 + i f/B}, \qquad \lvert H(B) \rvert = \frac{G}{\sqrt2}.\]Each tone is multiplied by \(H(f)\), so it is amplified and turned back in phase, by 45° at the bandwidth. The amplifier adds its own input noise \(e_n\) (V/√Hz) before its gain:
\[S_\text{out}(f) = \lvert H(f)\rvert^2\left(S_\text{in}(f) + e_n^2\right).\]When the output’s peak would pass the output limit, the amplifier says so: it would clip. The signal it hands on is not clipped. An input that is a current (a bare photodiode’s) is read as volts, and the amplifier notes it: a transimpedance amplifier is the block for a current.
Settings
| Field | Default | Meaning |
|---|---|---|
gain | 10 | Gain (V/V) |
bw | 1000000 | Bandwidth (Hz) |
en | 5 | Input noise (nV/√Hz) |
vmax | 10 | Output limit (V) |
From the tool's own tables, file format version 1: the names are those in a .jekray file.
Readouts
The panel gives its output in the steady state: the DC level, the five strongest tones (each one’s amplitude, rms and the phase of its cosine), and the noise, as a density at 1 kHz and in rms from 1 Hz to 1 GHz. Any notes, such as an input left unwired or an output past its limit, are listed under it.
Assumptions
- One pole: no second pole, no peaking and no slew-rate limit.
- Linear up to its limit, and not clipped past it, only flagged.
- Its input noise is white: no 1/f corner.