Instruction manual

LPA1 • 10
Feedback Circuit:
Your Ramsey LPA1 Power Booster Amplifier has been designed to give you
great amplification over a wide range of frequencies. Included in the design
of the circuit is a feedback loop consisting of the parts R8 and C5. You must
decide whether or not to include the feedback circuit into your kit.
According to the table below, with the feedback circuit in place, you may
experience a lower gain at frequencies up to 500Mhz. However, you will
note that this gain is relatively steady over this range. The loop also provides
slightly higher gain above 500Mhz. Please consider carefully which
frequency you are using and how much gain you require from the circuit.
Installing the feedback circuit has proven to add more circuit stability and
immunity to spurious signals. If you are experiencing difficulty with spurious
signals, it is a good idea to install the feedback circuit.
A good rule of thumb is to complete the circuit including the feedback circuit.
If you need more gain at lower frequencies, you are then able to remove the
feedback components.
Amplifier gain vs. frequency
Frequency
(Mhz)
Gain (dB)
w/o feedback
Gain
w/o feedback
Gain (dB)
w/ feedback
Gain
w/ feedback
10
36.4 4365 30 1000
50
35.7 3715 29.6 912
100
34.4 2754 28.9 776
200
30.6 1148 28.7 741
300
26.8 479 27 501
400
24.2 263 25.5 355
500
22 158 23.9 245
600
20.3 107 22.3 170
700
17.4 55 18.6 72
800
15.7 37 16.6 46
900
16.5 45 16.9 49
1000
16 40 16.4 44