An analog circuit with high sensitivity tends to change its behavior with varying temperature. Therefore all temperature sensitive components in the amplifying section of the circuit have been avoided.
Here a feedback amplifier with a gain close to 1 is needed. It is essential that its gain over the amplitude has its maximum at the working point. This is the only way to run an amplifier with highest sensitivity in a stable fashion. FETs show an increasing gain with increasing current. Operating close to the point of self-oscillation will lead to instability. Any pulse with higher amplitude will increase the gain. Diodes are used to compensate this unwanted increase in gain. The data of diodes are very temperature-dependend. This behavior is extremely well known. Therefore it is possible to completely compensate for this by changing the bias of the damping diodes.
To test our sensors under the harshest environmental conditions, the IFA has tested an evaluation module of our electronics at up to 70 °C and an air humidity of 95%. Water ran down the walls of the climate chamber and the electronic device as well. The sensitivity of the sensor was stable and constant.
The temperatures that we use in our lab for testing are higher. (We love safety.) Since we cannot apply humidity in a controlled way, we are very glad that this test has been carried out in such a challenging way and still had a positive outcome. After all, we are very glad with the minute procedures at the IFA. The stricter the testers the surer we can be that an approved technology functions under all circumstances.