diff --git a/content/zettels/current_amplifier.md b/content/zettels/current_amplifier.md
new file mode 100644
index 0000000..3405318
--- /dev/null
+++ b/content/zettels/current_amplifier.md
@@ -0,0 +1,20 @@
++++
+title = "Current Amplifier"
+author = ["Thomas Dehaeze"]
+draft = false
++++
+
+Tags
+: [Electronics]({{< relref "electronics" >}}), [Voice Coil Actuators]({{< relref "voice_coil_actuators" >}})
+
+
+## Current Amplifier to drive Inductive Loads {#current-amplifier-to-drive-inductive-loads}
+
+
+### Manufacturers {#manufacturers}
+
+| Manufacturers | Links | Country |
+|---------------|-------|---------|
+|               |       |         |
+
+<./biblio/references.bib>
diff --git a/content/zettels/voltage_amplifier.md b/content/zettels/voltage_amplifier.md
index d262983..4671f4d 100644
--- a/content/zettels/voltage_amplifier.md
+++ b/content/zettels/voltage_amplifier.md
@@ -12,7 +12,7 @@ Tags
 : [Signal to Noise Ratio]({{< relref "signal_to_noise_ratio" >}}), [Piezoelectric Actuators]({{< relref "piezoelectric_actuators" >}}), [Electronics]({{< relref "electronics" >}})
 
 
-## Voltage Amplifiers to drive Capacitive Load {#voltage-amplifiers-to-drive-capacitive-load}
+## Voltage Amplifiers to drive Capacitive Loads {#voltage-amplifiers-to-drive-capacitive-loads}
 
 
 ### Manufacturers {#manufacturers}
@@ -20,11 +20,11 @@ Tags
 | Manufacturers       | Links                                                                                                                                                   | Country     |
 |---------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------|-------------|
 | Piezo Drive         | [link](https://www.piezodrive.com/drivers/)                                                                                                             | Australia   |
-| Thorlabs            | [link](https://www.thorlabs.com/navigation.cfm?guide%5FID=2085)                                                                                         | USA         |
+| Falco System        | [link](https://www.falco-systems.com/products.html)                                                                                                     | Netherlands |
 | PI                  | [link](https://www.pi-usa.us/en/products/controllers-drivers-motion-control-software/piezo-drivers-controllers-power-supplies-high-voltage-amplifiers/) | USA         |
+| Thorlabs            | [link](https://www.thorlabs.com/navigation.cfm?guide%5FID=2085)                                                                                         | USA         |
 | Micromega Dynamics  |                                                                                                                                                         | Belgium     |
 | Lab Systems         | [link](https://www.lab-systems.com/products/amplifier/amplifier.html)                                                                                   | Isreal      |
-| Falco System        | [link](https://www.falco-systems.com/products.html)                                                                                                     | Netherlands |
 | Piezomechanics      | [link](https://www.piezomechanik.com/products/)                                                                                                         | Germany     |
 | Cedrat Technologies | [link](https://www.cedrat-technologies.com/en/products/piezo-controllers/electronic-amplifier-boards.html)                                              | France      |
 | Trek                | [link](https://www.trekinc.com/products/HV%5FAmp.asp)                                                                                                   | USA         |
@@ -38,9 +38,9 @@ Tags
 
 The piezoelectric stack can be represented as a capacitance.
 
-Let's take a capacitance driven by a voltage amplifier (Figure [1](#orgf2b344c)).
+Let's take a capacitance driven by a voltage amplifier (Figure [1](#org4297943)).
 
-<a id="orgf2b344c"></a>
+<a id="org4297943"></a>
 
 {{< figure src="/ox-hugo/voltage_amplifier_capacitance.png" caption="Figure 1: Piezoelectric actuator model with a voltage source" >}}
 
@@ -60,7 +60,7 @@ Thus, for a specified maximum current \\(I\_\text{max}\\), the "power bandwidth"
 -   Above \\(\omega\_{0, \text{max}}\\), the maximum current \\(I\_\text{max}\\) is reached and the maximum voltage that can be applied decreases with frequency:
     \\[ U\_\text{max} = \frac{I\_\text{max}}{\omega C} \\]
 
-The maximum voltage as a function of frequency is shown in Figure [2](#org1190638).
+The maximum voltage as a function of frequency is shown in Figure [2](#orgb578cd2).
 
 ```matlab
 Vpkp = 170; % [V]
@@ -74,7 +74,7 @@ C = 1e-6; % [F]
 56.172
 ```
 
-<a id="org1190638"></a>
+<a id="orgb578cd2"></a>
 
 {{< figure src="/ox-hugo/voltage_amplifier_max_V_piezo.png" caption="Figure 2: Maximum voltage as a function of the frequency for \\(C = 1 \mu F\\), \\(I\_\text{max} = 30mA\\) and \\(V\_{pkp} = 170 V\\)" >}}
 
@@ -88,7 +88,7 @@ If driven at \\(\Delta U = 100V\\), \\(C = 1 \mu F\\) and \\(I\_\text{max} = 1 A
 
 ### Bandwidth limitation (small signals) {#bandwidth-limitation--small-signals}
 
-This is takken from Chapter 14 of ([Fleming and Leang 2014](#org2e80fee)).
+This is takken from Chapter 14 of ([Fleming and Leang 2014](#orgd3659c0)).
 
 ```matlab
 L = 250e-9; % Cable inductance [H]
@@ -112,6 +112,15 @@ Specifications are usually:
 The bandwidth can be estimated from the Maximum Current and the Capacitance of the Piezoelectric Actuator.
 
 
+### Problem to drive highly capacitive loads {#problem-to-drive-highly-capacitive-loads}
+
+At high frequency, the impedance of the capacitive load is very small.
+This can pose several problems:
+
+-   the current to be supplied by the amplifier to have some voltage becomes very large
+-   the internal impedance of the amplifier may be large compared to the load impedance, and thus large voltage drop will occur
+
+
 ## Bibliography {#bibliography}
 
-<a id="org2e80fee"></a>Fleming, Andrew J., and Kam K. Leang. 2014. _Design, Modeling and Control of Nanopositioning Systems_. Advances in Industrial Control. Springer International Publishing. <https://doi.org/10.1007/978-3-319-06617-2>.
+<a id="orgd3659c0"></a>Fleming, Andrew J., and Kam K. Leang. 2014. _Design, Modeling and Control of Nanopositioning Systems_. Advances in Industrial Control. Springer International Publishing. <https://doi.org/10.1007/978-3-319-06617-2>.