Difference between revisions of "RF-Amp"

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[[file:RF_Amp_Schematic-4.PNG]]
 
[[file:RF_Amp_Schematic-4.PNG]]
 
=== Input/Output Transformer ===
 
 
==== FT37-43 Toroid ====
 
 
* [http://toroids.info/FT37-43.php FT37-43]
 
* Wideband Transformers 5 - 400 MHz
 
* Power Transformers 0.5 - 30 MHz
 
* 10 turns = 35uH
 
 
[[file:FT37-43_10_Turns.PNG]]
 
 
==== Tracks ====
 
 
[[file:RF-Amp-tracks.PNG]]
 
 
==== Input Transformer ====
 
 
** Input Transformer (T1 on Charlie's - T2 on this board)
 
***  50:75.8 Ohms = 1 : 1.23 turns ratio
 
**** 9 turns primary, 11 turns on secondary
 
 
[[file:RF-Amp-T2.PNG]]
 
 
==== Output Transformer ====
 
 
** Output transformer (T2 on Charlie's - T1 on this board)
 
*** 200:50 Ohms = 2:1 turns ratio
 
*** 10 turns primary (on transistor collector), 5 turns secondary (towards output)
 
 
[[file:RF-Amp-T1.PNG]]
 
  
 
== LT Spice Simulation ==
 
== LT Spice Simulation ==

Revision as of 11:11, 6 November 2021

RF-Amp Front.png

RF Amplifier Features

RF Amplifier Design

Schematic

RF Amp Schematic-4.PNG

LT Spice Simulation

Transformers

RF-AMP-LTSPICE XFMRS.PNG

Charlie Morris Design

Beta DC

  • Geometric mean min/max beta at operating current
    • =sqrt(100*300) = 173

Beta AC

  • Gain bandwidth product divided by operating frequency
    • Assume operating frequency of 10 MHz (my IF is actually at 9 MHz)
    • = 300/10 = 30

DC Operating Point

  • CE current 10 mA
    • If Vce = 6V, this is 60 mW power dissipation
  • Assume Ve (voltage across emitter resistor) = 1/10 Vcc = 12V/10 = 1.2V
      • R3 is Re (emitter resistor) = 1.2V/0.01A = 120 ohms
  • VCE = 0.7V (typical from data sheet)
  • V(emitter) = 1.2V
  • V(base) = V(emitter) + VCE = 1.9V
  • Assume current in biasing resistors = 10x current needed by DC beta
    • 10 mA in C-E, beta DC less = 10 mA/173 = 48 uA
    • 10x the current in the biasing resistors = 480 uA (calculated)
  • R2 is 1.9V at 480 uA = 3.9K use 3.3K
    • Actual current will be 1.9V/3.3 ohms = 634 mA
  • R1 sources current to R2 and transistor base
    • Voltage = Vcc (12V) - 1.9V = 10.1V
    • Current = 576 uA + 57 uA = 634 uA
    • R1 = 10.1 / .634 mA = 15.9K, use 15k

Input resistance

  • Parallel resistors R1, R2 paralleled with transistor input impedance
    • R1=15K, R2=3.3K
    • Transistor resistance = Beta AC (30) times re
      • re = 26 / Ie (10 mA in mA) = 26/10 =
      • Beta AC * re = 30*2.6 = 78 ohms - predominates
    • All in parallel are 75.8 ohms

Transformers

  • T1 50:75.8 ohms
    • n = sqrt(Zout/Zin) = sqrt(75.8/50) = 1.23
    • 9:11 turns ratio
  • T2 - different than Charlie's design since my Crystal filters are all 50 ohms in/out
    • 250:50 ohms
    • n = sqrt(250/50) = 2.23:1
    • 11:5 turns

Charlie's Notes

IF Amp 0046A.jpg

IF Amp 0046B.jpg

IF Amp 0046C.jpg

IF Amp 0047A.jpg

IF Amp 0047B.jpg

IF Amp 0047C.jpg

Video

Assembly Sheet