Update Content - 2022-10-27

content/zettels/transimpedance_amplifiers.md

@@ -16,6 +16,35 @@ A transimpedance amplifier is a "current to voltage converter" and is also named
 It is generally used to interface a sensor which outputs a current proportional to the measurement parameter ([Quadrant Photodiodes]({{< relref "quadrant_photodiodes.md" >}}) for instance).
 
 
+## Basic Circuit {#basic-circuit}
+
+A basic transimpedance amplifier circuit is shown in Figure [1](#figure--fig:transimpedance-amplifier-schematic).
+
+It produces an output voltage \\(V\_{\text{out}}\\) proportional to the input current \\(I\_{\text{sig}}\\):
+
+\begin{equation}
+\boxed{V\_{\text{out}} = -I\_{\text{sig}} R\_f}
+\end{equation}
+
+The gain of the amplifier is simply \\(-R\_f\\) in [V/A].
+
+The feedback resistor creates a Johnson noise that corresponds to a current noise:
+
+\begin{equation}
+i\_{n} = \sqrt{4kT/R\_f} \quad [A/\sqrt{Hz}]
+\end{equation}
+
+This is usually larger than the amplifier input current noise.
+
+<a id="figure--fig:transimpedance-amplifier-schematic"></a>
+
+{{< figure src="/ox-hugo/transimpedance_amplifier_schematic.png" caption="<span class=\"figure-number\">Figure 1: </span>Transimpedance Amplifier; Current in, Voltage out" >}}
+
+More information about transimpedance can be found in [The art of electronics - third edition]({{< relref "horowitz15_art_of_elect_third_edition.md" >}}), chapter 8.11.4, especially on the trade-off between gain, noise and bandwidth.
+
+See [this](https://www.hardware-x.com/article/S2468-0672(21)00062-6/fulltext) open hardware design.
+
+
 ## Manufacturers {#manufacturers}
 
 | Manufacturers                                                                                              | Country |
@@ -24,6 +53,7 @@ It is generally used to interface a sensor which outputs a current proportional
 | [MMF](https://www.mmf.de/signal_conditioners.htm)                                                          | Germany |
 | [Femto](https://www.femto.de/en/products/current-amplifiers.html)                                          | Germany |
 | [FMB Oxford](https://www.fmb-oxford.com/products/controls-2/control-modules/i404-quad-current-integrator/) | UK      |
+| [Thorlabs](https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=7083)                                 | UK      |
 
 
 ## Bibliography {#bibliography}