The Norton amplifier has very nice performance. It is class of CATV amplifier. Gain is flat over a frequency decade or more. The gain is selected by turns ratio in the collector circuit tap.
For VHF the input impedance needs some match. The isolation s12 is good up to few hundreds MHz. It can work in broadband mode from (2 to 200) MHz. First Norton amplifier I made for 2m band transceiver. It was pain and finally it worked.
The lower frequency side limit is set by the transformer inductance, magnetic flux, leakage inductance, and capacitors.
The upper frequency side limit is set by the ferrite transformer, collector capacitance, s21, and transmission line length. It can cover decade or two. The noise figure is good. Location of max gain and minimum noise figure are never identical.
Common base configuration has extended dynamic range in terms of IP3, IP2, IMD, compared to common emitter configuration. It is the system architecture. Output power is limited by ferrite core, Vcc, quiescent current, temperature, and power delivered by the transistor.
!! Do not burn your receiver with Norton amplifier test setup. !!
Check published schematic diagrams with broadband common emitter LNA.
It is the Dutch "Hottentot" design.
Since first test with IP3 tester and Spectrum Analyzer, you start to understand.
Please do not use "SIDOL" to polish your transistors.
The transformer turns ratio is:
N = M2 - M -1.
N ... collector to output tap turns
M ... output tap to Vcc, turns
E emitter input ... one turn, for lower gain oriented
gain = m2; [linear number]
Gain = 10 * Log10(m2); [dB]
There is only one gain in [dB]. Doesn't matter if it comes from voltage or power. Some California experts claim the numbers for voltage and power are different. It is possible. It is named "The Obermayer's space warp black hole anomalies". If you hear Six Sigma nonsense and mean response, it is NCDXF.
( Voltage gain [dB] = Power gain [dB], same impedances)
G = 20. log10(V1/V2) [dB]; voltage
g = 10. log10(p1/p2) [dB]; power
magnet wire diameter about 0.25mm - 0.2mm.
Vcc = 12 to 15V, Vces=0.5V, Ic= 25mA, heatsink, 2N5109 from Central Semiconductor, NY.
E [turns] M [turns] N [turns] nominal Gain [dB] 1 2 1 6.02 1 3 5 9.54 1 4 11 12.04 1 5 19 13.9 1 6 29 15.56
N = M2 - M -1.
The E-emitter input has one turn. If you swap the input wires, the amplifier will give higher gain - that means oscillation. Keep the lower gain.
The collector turns "N" ratio commands the gain. "M" goes to the Vcc. Select gain of 6 dB, 9 dB, 12 dB, 14dB and expect 0.5dB loss in ferrite core. Consider the input transients from antenna with amplitude of Volts, ESD, and lightning. RF medium power bipolars 5 Watts in metal case are more rigid for this application. The 5-7GHz transitors have mostly unstable s-parameter matrix in the HF 30 MHz region.
You might find similar designs with feedback in common emmiter config. There are another three similar amplifier configurations with transformer used for cable TV networks. I compared 2N5109 with 2N2222 metal case. The 2N2222 0.5W is bit lazy, requiring higher current to get the gain-bandwith product. It has higher rbb resistance.
The metal case transistors are better than the plastic ones. There was a difference of 6-8 dB in IMD3 between the plastic and metal case 2N2222. The plastic ones have higher thermal resistance. The input was from IMD3 tester delivering two-tones. Output measured with HP Spectrum Analyzer.
Transistor selection can be BFR34, BFR96, bfw16, bfw30, 2sc3355, 2SD636, 2n3725, 2N3866, and so on. Check for stability from s-parameters. The documented s-paramenters start at 500MHz. Noise figure on HF won't make a difference. The BFW16A/KFW16A broadband transistor has 3dB lower intermodulations compared to 2N5109. The IMD3 levels drop with lower gain, larger current, higher Vcc, and better linearity transistor. Use of higher Vcc improves the IP3 in single digit [dB], not much.
Ferrite limits are - maximum magnetic flux and the resulting core linearity. Inappropriate ferite core can screw you amplifier performance. If you handle low signal levels such as e.g. -84dBm and low noise floor, Norton amplifier shall be shielded. During power-up, the output transformer provides positive pulse.
Some sensitive HP EMI Spectrum Analyzers with LCD display have limits for IP3 reading and finite IMD3 floor. Check how the Spectrum Analyzer works with two-tones. Then measure the external amplifier.
There is another method how to measure the signal distortion using the EVM meter - error vector magnitude.
Ordinary bipolars are better than specialized HBT chips in special case, with special footprint, and becoming obsolete in multiple months by speculative marketing practices.
Somebody thinks there will be no IMD3 distortion in the SDR-DSP receiver unit. It is naivety and lack of information.
Norton amplifier ARRL.pdf
Resources:
[1] VA3DIW' notes
[2] Lankford: Common Base Transformer Feedback Norton Amplifiers
[3] U.L. Rohde: Digital PLL Sythesizers
[4] Futurelek.com - smd and leaded RF transistors
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