Noise measurements of several PNP transistors. (For NPN transistors, see part3
)
On this page, the noise performance of several PNP transistors is tested.
Figure 1, this is the amplifier I use for measuring the noise of a
PNP transistor.
The circuit is very similar to the circuit used for measuring NPN transistors
which you find in part3 ,
where you can find some information on the working of the circuit.
This PNP version works on -12 volt, while the NPN version works on +12 volt.
Therefore the polarity of the electrolytic capacitors and diode D1 is reversed.
Figure 2, the amplifier for measuring the PNP transistor noise.
The transistor under test is hanging on the three green wires.
Transistor type
Manufacturer
View datasheet
of transistor
hfe
at 25°C
Ic=10 mA
Measured input noise
of test amplifier
at 1 kHz, Ic =10 mA.
nV/√Hz
Calculated transistor
base resistance
Rbb
(Ω)
Calculated Input noise
of only the transistor.
(R_circuit = 0Ω)
at 1 kHz, Ic=10 mA.
nV/√Hz
This table gives an overview of the transistors tested, with the measured input voltage
noise of the test amplifier, and the calculated base resistance Rbb of the
transistors.
Also the voltage noise of only the transistor is calculated at 10 mA collector
current.
For an explanation of the Rbb value, see
part 4 .
For more info about the testing method, see
part 1 and
part 2 .
The collector current of the transistors is in all cases 10 mA.
For all transistors, the Rbb value was determined from the noise at 1 kHz.
In the next figure, the input noise voltages of all measured transistors are plotted in
one diagram.
Figure 3, input noise voltage of the test setup, with different input transistors.
For this diagram, I compensated the values for the frequency response of the
test setup.
Figure 4 shows the test setup response, and the compensation I applied for
making figure 3.
Figure 4, frequency response of test setup, and the compensation curve.
