tags: noise source, zener, BFR93A
Some modifications of the broadband noise source presented previously. This second version is based on a two-stage amplifier, with the same BFR93A transistors. The difference here is that the amplifier is supplied with + 12V in order to use a 7812 regulator both for the amplifier but also for the zener diode. The stable and fixed voltage of these two parts is large enough to have a constant noise level. The zener diode used is Panasonic DZ2409100L of 9.1 V in a SMD box.
It can be seen that the voltage amplification of this version is greater, of the order of 25 dB in a 50 ohm load.
The realization is made in the same way, on a plate with hole with a good ground plane (important for the RF) which is in contact with the regulator 7812.
Finally everything is put in an aluminum box. The anodization of the case has been removed from the connections to improve the shielding.
We see that the PSD of the spectrum analyzer (HP8594E) without the noise source is -135 dBm / Hz. With the source on, however, the noise floor rises and displays a PSD that goes from -105 dBm / Hz at 1 MHz to -130 dBm / Hz at 200 MHz, which represents an ENR of up to 69 dB compared to the floor thermal of -174 dBm / Hz.