View source for Kits and Parts Universal Wideband Small Signal RF Amplifier

[[file:K&P_RF_Amp_P1903-720px.jpg]]

== Specs ==

* [https://kitsandparts.com/rfamp1.4.php Kits and Parts Universal Wideband Small Signal RF Amplifier]
* Spec: 22+ dBm power gain from 2-30 MHz
** Measured +25-27 dBm gain - fairly flat response
** +20 dBm gain up to 80 MHz
* 50 ohm input and 50 ohm output.
* 100 milliwatt maximum output.
* 0.031A at 12V = 370mW

== Schematic ==

* [https://www.onsemi.com/pdf/datasheet/2sc5551a-d.pdf 2SC5551A Datasheet]

[[file:rfampsch1.4.png]]

=== Transformer ===

* [https://toroids.info/FT37-43.php FT37-43 Toroid]

[[file:FT37-43_10_TURNS.PNG]]

== LTSPICE Simulation ==

* [http://ltwiki.org/index.php?title=Standard.bjt 2SC5551A LTSPICE Model]

.model 2SC5551A NPN(IS=4.58f BF=150 NF=1.003 VAF=35 IKF=1.2 ISE=5f NE=1.6 BR=35 NR=1.001 VAR=20 IKR=10.98m ISC=255.9f NC=1.5 RB=1.5 IRB=300.0m RBM=300m RE=280m RC=1.25 XTB=0 EG=1.11 XTI=3 CJE=2.36p VJE=199.0m MJE=73.20m TF=30.50p XTF=13.45m VTF=280.0m ITF=25.80m PTF=25.7 CJC=3.08p VJC=520.0m MJC=380.8m .15m TR=1.38n FC=1.51m )

* Without transformer

[[file:K&P_LTSPICE_RF_AMP.PNG]]

* With transformer

[[file:K&P_LTSPICE_RF_AMP_TRANSFORMER.PNG]]

== PCB ==

[[file:rfamppcb1.4.png]]

[[file:miniboard3.png]]

== Build Instructions ==

# Align the SMD 2SC5551A RF Transistor onto Q1 pad in the center of the PCB. Using a temperature controlled solder pencil, solder without overheating.
# Align the four 100n SMD capacitors on the PCB and solder.
# Install resistors R1, R2, R3 and R4 on the PCB and solder.
# Install Toroids Transformer T1, Twist the Red & Green wires together to about 4 twists per inch.    Wind 10 turns of the twisted wires onto the toroid. The magnet wire is heat stripable; trim each wire end to 3/4 inches. Prepare the toroid wires for soldering.
# Magnet Wire Soldering Details Here:    One of each colored wires connects under the toroid and one of each colored wires connects on the outside of the toroid. One color wire should connect to J3/C4 and the other color connects to Q1. You should also have 2 different color wires connecting under the toroid via a PCB trace.
# R5,6,7 (not included) are used to attenuate the rf output. Place a jumper wire across R6.
# Connect the RF Amplifier via J1(input), J2(output) and J3(power).

== NanoVNA Measurements ==

* Tried [[RF_Attenuators#Triple_Attenuator|30 dB Attenuator]] in and out sides of RF Amplifier with somewhat different results

=== Attenuator Before Amp ===

* [[NanoVNA]]
** Sweep settings, Attenuator in port CH1 (s21) in dB: 30.0
* [[RF_Attenuators#Triple_Attenuator|Attenuator]] - 30 dB
** Below are with 30 dB attenuator between [[NanoVNA]] CH0 (output) and RF Amp input
* Built four Amplifier cards, identical results

==== At 1, 9 and 30 MHz ====

* 30 dB attenuator between [[NanoVNA]] CH0 (output) and RF Amp input

[[file:K&P_LTSPICE_RF_AMP_NanoVNA_1MHz-30MHz_at3Points.PNG]]

==== S21 Gain ====

* 30 dB attenuator between [[NanoVNA]] CH0 (output) and RF Amp input

[[file:K&P_LTSPICE_RF_AMP_NanoVNA_1MHz-30MHz_S21-Gain.PNG]]

==== SWR ====

* 30 dB attenuator between [[NanoVNA]] CH0 (output) and RF Amp input
* Very good match into attenuator (as would be expecteed)

[[file:K&P_LTSPICE_RF_AMP_NanoVNA_1MHz-30MHz_SWR.PNG]]

==== 1-100 MHz Sweep ====

[[file:K&P_RF_AMP_NanoVNA_1MHz-100MHz_at3Points.PNG]]

[[file:K&P__RF_AMP_NanoVNA_1MHz-100MHz_S21-Gain.PNG]]

=== Attenuator After Amp ===

* 30 dB attenuator between [[NanoVNA]] CH0 (output) and RF Amp input
* 20 dB gain at 80 MHz

==== At 1, 9 and 30 MHz ====

* [[NanoVNA]]
** Repeated with 30 dB attenuator between  RF Amp output and the [[NanoVNA]] CH1 (input)
* [[RF_Attenuators#Triple_Attenuator|Attenuator]] - 30 dB

[[file:K&P_RF_AMP_NanoVNA_1MHz-30MHz_at3Points_AttenOut.PNG]]

==== S21 Gain ====

* 1-30 MHz scan

[[file:K&P__RF_AMP_NanoVNA_1MHz-30MHz_S21-Gain_AttenOut.PNG]]

==== SWR ====

* Not as great (still OK) match into actual input (without attenuator)

[[file:K&P__RF_AMP_NanoVNA_1MHz-30MHz_SWR_AttenOut.PNG]]

==== 1-100 MHz ====

[[file:K&P_RF_AMP_NanoVNA_1MHz-100MHz_at3Points_AttenOut.PNG]]

[[file:K&P_RF_AMP_NanoVNA_1MHz-100MHz_S21-Gain_AttenOut.PNG]]

[[file:K&P_RF_AMP_NanoVNA_1MHz-100MHz_SmithChart_AttenOut.PNG]]

== References ==

* [http://leleivre.com/rf_pipad.html PI Attenuator Calculator]
* [https://www.pasternack.com/t-calculator-pi-attn.aspx Pi Attenuator Calculator]