Difference between revisions of "RF-Amp"

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[[file:RF_Amp_Schematic-4.PNG]]
 
[[file:RF_Amp_Schematic-4.PNG]]
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=== DC Operating Point ===
 
−
 
−
* Ice = 10 mA
 
−
* Ve = 0.1 * Vcc = 1.2V
 
  
 
=== Input/Output Transformer ===
 
=== Input/Output Transformer ===
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[[File:RF-AMP-LTSPICE_XFMRS.PNG]]
 
[[File:RF-AMP-LTSPICE_XFMRS.PNG]]
  
−
== Charlie Morris Schematics ==
+
== Charlie Morris Design ==
  
−
* From [https://zl2ctm.blogspot.com/2020/11/go-qrp-portable-ssb-rig.html Charlie Morris' (ZL2CTM) Go QRP Portable SSB Rig]
+
* From Charlie's notes with mods for my use
 +
** [https://zl2ctm.blogspot.com/2020/11/go-qrp-portable-ssb-rig.html Charlie Morris' (ZL2CTM) Go QRP Portable SSB Rig]
 +
* [https://www.mouser.com/datasheet/2/308/1/2N3903_D-2310199.pdf 2N3904 data sheet]
  
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=== IF AMP ===
+
=== Beta DC ===
  
−
* From Charlie's notes
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* Geometric mean min/max beta at operating current
−
** DC Operating Point = 10 mA
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** =sqrt(100*300) = 173
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** V(emitter resistor) = 1/10 Vcc = 1.2V
+
 
−
*** R(emitter resistor) = 1.2V/0.01A = 120 ohms
+
=== Beta AC ===
−
* Beta DC = geometric mean min/max beta at operating current
+
 
−
** = sqrt(100*300) = 173
+
* Gain bandwidth product divided by operating frequency
−
* Beta AC = gain bandwidth product divided by operating frequency
 
 
** Assume operating frequency of 10 MHz (my IF is actually at 9 MHz)
 
** Assume operating frequency of 10 MHz (my IF is actually at 9 MHz)
 
** = 300/10 = 30
 
** = 300/10 = 30
−
* VCE = 0.7V
+
 
 +
=== 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(emitter) = 1.2V
 
* V(base) = V(emitter) + VCE = 1.9V
 
* V(base) = V(emitter) + VCE = 1.9V
 
* Assume current in biasing resistors = 10x current needed by DC beta
 
* Assume current in biasing resistors = 10x current needed by DC beta
 
** 10 mA in C-E, beta DC less = 10 mA/173 = 48 uA
 
** 10 mA in C-E, beta DC less = 10 mA/173 = 48 uA
−
** 10x the current in the biasing resistors = 480 uA
+
** 10x the current in the biasing resistors = 480 uA (calculated)
 
* R2 is 1.9V at 480 uA = 3.9K use 3.3K
 
* R2 is 1.9V at 480 uA = 3.9K use 3.3K
−
* R1 sources current to R2 and BE junction
+
** 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
 
** Voltage = Vcc (12V) - 1.9V = 10.1V
−
** Current = 480 uA + 48 uA = 528 uA
+
** Current = 576 uA + 57 uA = 634 uA
−
** R1 = 10.1 / .528 mA = 19K, use 15k
+
** R1 = 10.1 / .634 mA = 15.9K, use 15k
−
* Input resistance - parallel resistors R1, R2 paralleled with transistor input impedance
+
 
 +
=== Input resistance ===
 +
 
 +
* Parallel resistors R1, R2 paralleled with transistor input impedance
 
** R1=15K, R2=3.3K
 
** R1=15K, R2=3.3K
 
** Transistor resistance = Beta AC (30) times re
 
** Transistor resistance = Beta AC (30) times re
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*** Beta AC * re = 30*2.6 = 78 ohms - predominates
 
*** Beta AC * re = 30*2.6 = 78 ohms - predominates
 
** All in parallel are 75.8 ohms
 
** All in parallel are 75.8 ohms
 +
 +
=== Transformers ===
 +
 
* T1 50:75.8 ohms
 
* T1 50:75.8 ohms
 
** n = sqrt(Zout/Zin) = sqrt(75.8/50) = 1.23
 
** n = sqrt(Zout/Zin) = sqrt(75.8/50) = 1.23
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** n = sqrt(250/50) = 2.23:1
 
** n = sqrt(250/50) = 2.23:1
 
** 11:5 turns
 
** 11:5 turns
 +
 +
=== Charlie's Notes ===
  
 
[[FILE:IF Amp_0046A.jpg]]
 
[[FILE:IF Amp_0046A.jpg]]

Revision as of 11:11, 6 November 2021

RF-Amp Front.png

RF Amplifier Features

RF Amplifier Design

Schematic

RF Amp Schematic-4.PNG

Input/Output Transformer

FT37-43 Toroid

  • FT37-43
  • Wideband Transformers 5 - 400 MHz
  • Power Transformers 0.5 - 30 MHz
  • 10 turns = 35uH

FT37-43 10 Turns.PNG

Tracks

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

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)

RF-Amp-T1.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

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