Difference between pages "RF Attenuators" and "AudioAmp380"

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== Purchased Attenuators ==
+
[[FILE:AudioAmp380-3D.png]]
  
−
=== Programmable Attenuator ===
+
== Design ==
  
−
* [[PE4302 RF Attenuator|PE4302 RF Attenuator board in my enclosure design]]
+
* Pre-amp plus power amp
 +
* 50 Ohm input impedance
 +
* Gain trimmer potentiometer on preamp
 +
* External mount gain potentiometer
 +
* [https://www.ti.com/lit/ds/symlink/ne5534.pdf ] Pre-amplifier
 +
* [https://www.ti.com/lit/ds/symlink/lm380.pdf LM380] 2.5W Audio Power Amplifier
 +
* 12V nominal power
 +
** 10-22V
 +
* Fits into 80x50x20mm extruded aluminum enclosure
 +
`
 +
=== Pre-Amplifier (NE5534) ===
  
−
[[file:PE4302_P1833-720px.jpg]]
+
* Low-Noise Operational Amplifiers
 +
* Equivalent Input Noise Voltage 3.5 nV/√Hz Typ
 +
* Unity-Gain Bandwidth 10 MHz Typ
 +
* Common-Mode Rejection Ratio 100 dB Typ
 +
* Wide Supply-Voltage Range ±3 V to ±20 V
 +
* Used as single supply
  
−
=== Triple Attenuator ===
+
=== Audio Power Amplifier (LM380) ===
  
−
* [[0/10/20/30 dB Attenuator]]
+
* Wide Supply Voltage Range: 10V-22V
 +
* Low Quiescent Power Drain: 0.13W (VS= 18V)
 +
* Voltage Gain Fixed at 50 (34 dB)
 +
* High Peak Current Capability: 1.3A
 +
* Input Referenced to GND
 +
* High Input Impedance: 150kΩ
 +
* Low Distortion
 +
* Quiescent Output Voltage is at One-Half of the Supply Voltage
  
−
[[file:ATTEN4_CHINA_PCB.PNG]]
+
== Controls ==
  
−
== Homebrew RF Attenuators ==
+
* RV1 - trade-off book gain/bandwidth - Tune for best sound
 +
* RV2 - volume control (after preamp and before LM380 Amp). 1x5 header wire to external pot
 +
* J1 - Audio In, 50 Ohms input impedance
 +
* J2 - Audio Out, 8 Ohm speakers
 +
* J3 - Power, 10V-22VDC
  
−
[[file:Atten_30dB_20dV_P1812-720px.jpg]]
+
== Rev 2 Schematic ==
−
=== 30 dB Attenuator ===
 
  
−
* [http://leleivre.com/rf_pipad.html Pi Attenuator Calculator]
+
[[file:AudioAmp380-Schematic.png]]
  
−
[[file:Atten30dB_P116-720px.jpg]]
+
== Rev 1 Rework ==
  
−
[[file:30dB_Attenuator.PNG]]
+
* Issues
 +
** Front end opamp has + and - reversed
 +
** Also hooked up the feedback to the wrong input
 +
* Replace R1 with jumper
 +
* Replace C9 with jumper
 +
* Remove C2
 +
* 5 Cuts
 +
** 4 on front
 +
** 1 on back
 +
* 5 jumper segments on back
 +
** 2 nodes
  
−
* Built
+
[[file:U2-2_3_Rev1_Rev2_Cuts_Jumpers.png]]
−
** Standard 5% resistor values
 
−
** R1 = 820 in parallel with 22K = 790.6 ohms
 
−
** R2 = 2 paralleled 120 Ohm 1/4W resistors paralleled with 470 ohms = 53.2 ohms
 
−
** Flat from 0-30 MHz
 
−
** Measured attenuation is flat
 
−
*** -30.01dB at 1 MHz
 
−
*** -30.24dB at 30 MHz
 
−
** Input Impedance - 53.1 ohms, 21.3nF
 
−
** SWR 1.06
 
−
** 1/2W max (5VDC max, 0 ohm source)
 
  
−
* NanoVNA scan data
+
* Jumpers on rear side
  
−
[[file:30dB_Attenuator_NanoVNA_Setup_Curve_900MHz.PNG]]
+
[[file:AudioAmp380_Back_Jumpers.PNG]]
  
−
[[file:30dB_Attenuator_NanoVNA_Data_900MHz.PNG]]
+
== Videos ==
  
−
* LTSPICE Simulation
+
[[file:ZL2CTM_Schematic.PNG]]
  
−
[[file:LTSPice_30dB.PNG]]
+
<video type="youtube">GlT0HbvcmrM</video>
  
−
=== 20 dB Attenuator ===
+
== Assembly Sheet ==
  
−
[[file:Atten_20dB_P115-720px.jpg]]
+
[[LM380 Rev 1 Assembly Sheet]]
−
 
 
−
[[file:20dB_Attenuator.PNG]]
 
−
 
 
−
* Build
 
−
** Standard 5% resistor values
 
−
** R1 = 2 of 510 in parallel also in parallel with 8.2K = 247.3 ohms
 
−
** R2 = 2 paralleled 150 Ohm 1/2W resistors paralleled with 330 ohms = 61.11 ohms
 
−
** Flat from 0-30 MHz
 
−
** Measured attenuation is flat
 
−
** Input Impedance - tbd ohms, tbd nF
 
−
** SWR tbd
 
−
** 1W max (8.6 V max, 0 ohm source)
 
−
 
 
−
[[file:20dB_Attenuator_NanoVNA_Setup_Curve_900MHz.PNG]]
 
−
 
 
−
[[file:20dB_Attenuator_NanoVNA_Data_900MHz.PNG]]
 
−
 
 
−
* LTSPICE Simulation
 
−
 
 
−
[[file:LTSPice_20dB.PNG]]
 
−
 
 
−
=== Attenuator Construction ===
 
−
 
 
−
* Single side copper clad PCB
 
−
** Approx 2"x1"
 
−
* Clean with steel wool
 
−
* Solder SMA connectors
 
−
** Use large alligator clips to hold while soldering
 
−
** Solder on sides only
 
−
 
 
−
[[file:Atten_01_SMAs_720px.jpg]]
 
−
 
 
−
* Cut "T" Shaped pads
 
−
** I used nibbler
 
−
* Center fits between connector ground pins
 
−
* Glue down pads with Superglue
 
−
 
 
−
[[file:Atten_02_Pads_720px.jpg]]
 
−
 
 
−
* Solder center pin with big solder blob
 
−
** A bit too high for direct contact
 
−
* Verify raised pad does not short to ground
 
−
 
 
−
[[file:Atten_03_Solder CenterPads_720px.jpg]]
 
−
 
 
−
* Solder side resistor(s)
 
−
* Leave room for center resistor(s)
 
−
 
 
−
[[file:Atten_04_Solder Side_Resistors_720px.jpg]]
 
−
 
 
−
* Measure side resistors from pad to ground
 
−
* Should match value
 
−
* Solder center resistor(s)
 
−
 
 
−
[[file:Atten_05_Solder Center_Resistors_720px.jpg]]
 
−
 
 
−
* Verify no shorts between centers and ground
 
−
 
 
−
== Attenuator Design - Rev 2 ==
 
−
 
 
−
[[FILE:ATTEN.PNG]]
 
−
 
 
−
* SMA connectors
 
−
* Resistors
 
−
** 1206
 
−
*** 1/4W
 
−
** 1% values
 
−
 
 
−
[[file:10dB_Attenuator.PNG]]
 
−
 
 
−
=== Parts ===
 
−
 
 
−
{| class="wikitable"
 
−
! Mfr. #
 
−
! Manufacturer
 
−
! Customer #
 
−
! Qty
 
−
! R1/R2
 
−
! Description
 
−
|-
 
−
| RK73H2BTTE17R8F
 
−
| KOA Speer
 
−
| ATTEN_03DB
 
−
| 1
 
−
| R1
 
−
| Resistors - SMD 1/4W 17.8 ohms 1%
 
−
|-
 
−
| RC1206FR-07294RL
 
−
| YAGEO
 
−
| ATTEN_03DB
 
−
| 2
 
−
| R2
 
−
| Resistors - SMD 294 ohms 1/4W 1206 1%
 
−
|-
 
−
| RK73H2BTTD37R4F
 
−
| KOA Speer
 
−
| ATTEN_06DB
 
−
| 1
 
−
| R1
 
−
| Resistors - SMD 1/4W 37.4 ohms 1%
 
−
|-
 
−
| CRCW1206150RFKEAC
 
−
| Vishay
 
−
| ATTEN_06DB
 
−
| 2
 
−
| R2
 
−
| Resistors - SMD 1/4Watt 150 ohms 1%
 
−
|-
 
−
| RC1206FR-0771R5L
 
−
| YAGEO
 
−
| ATTEN_10DB
 
−
| 1
 
−
| R1
 
−
| Resistors - SMD 71.5 ohms 1/4W 1206 1%
 
−
|-
 
−
| RC1206FR-0797R6L
 
−
| YAGEO
 
−
| ATTEN_10DB
 
−
| 2
 
−
| R2
 
−
| Resistors - SMD 97.6 ohms 1/4W 1206 1%
 
−
|-
 
−
| RK73H2BTTD1070F
 
−
| KOA Speer
 
−
| ATTEN_13DB
 
−
| 1
 
−
| R1
 
−
| Resistors - SMD 1/4W 107 ohms 1%
 
−
|-
 
−
| RC1206FR-0778R7L
 
−
| YAGEO
 
−
| ATTEN_13DB
 
−
| 2
 
−
| R2
 
−
| Resistors - SMD 78.7 ohms 1/4W 1206 1%
 
−
|-
 
−
| AC1206FR-07249RL
 
−
| YAGEO
 
−
| ATTEN_20DB
 
−
| 1
 
−
| R1
 
−
| Resistors - SMD 249 ohms 1/4W 1206 1%
 
−
|-
 
−
| RK73H2BTTDD61R9F
 
−
| KOA Speer
 
−
| ATTEN_20DB
 
−
| 2
 
−
| R2
 
−
| Resistors - SMD 61.9 ohms 1%
 
−
|-
 
−
| RK73H2BTTD7870F
 
−
| KOA Speer
 
−
| ATTEN_30DB
 
−
| 1
 
−
| R1
 
−
| Resistors - SMD 1/4W 787 ohms 1%
 
−
|-
 
−
| AC1206FR-0753R6L
 
−
| YAGEO
 
−
| ATTEN_30DB
 
−
| 2
 
−
| R2
 
−
| Resistors - SMD 53.6 ohms 1/4W 1206 1%
 
−
|-
 
−
| RC1206FR-072K49L
 
−
| YAGEO
 
−
| ATTEN_40DB
 
−
| 1
 
−
| R1
 
−
| Resistors - SMD 2.49k ohms 1/4W 1206 1%
 
−
|-
 
−
| RK73H2BTTD51R0F
 
−
| KOA Speer
 
−
| ATTEN_40DB
 
−
| 2
 
−
| R2
 
−
| Resistors - SMD 1/4W 51 ohms 1%
 
−
|-
 
−
| RK73H2BTTDD49R9F
 
−
| KOA Speer
 
−
| ATTEN_50_60DB
 
−
| 2
 
−
| R2
 
−
| Resistors - SMD 49.9 ohms 1%
 
−
|-
 
−
| RC1206FR-077K87L
 
−
| YAGEO
 
−
| ATTEN_50DB
 
−
| 1
 
−
| R1
 
−
| Resistors - SMD 7.87k ohms 1/4W 1206 1%
 
−
|-
 
−
| RC1206FR-0726K1L
 
−
| YAGEO
 
−
| ATTEN_60DB
 
−
| 2
 
−
| R2
 
−
| Resistors - SMD 26.1k ohms 1/4W 1206 1%
 
−
|-
 
−
|}
 
−
 
 
−
=== Measurements ===
 
−
 
 
−
* NanoVNA
 
−
* S21 gain
 
−
* 1-900 MHz scan
 
−
* Calibrated with cable on thru
 
−
 
 
−
==== 40 dB Attenuator ====
 
−
 
 
−
* Flat from 1-600 MHz
 
−
* Higher attenuation past 600 MHz
 
−
* -39.9 dB at 14 MHz
 
−
* S21
 
−
 
 
−
[[file:ATTEN1_NanoVNA_40dB.png]]
 
−
 
 
−
* Flat from 1-30 MHz
 
−
* S21
 
−
 
 
−
[[file:ATTEN1_NanoVNA_40dB_1-30MHz.png]]
 
−
 
 
−
* s11
 
−
* 1-900 MHz
 
−
 
 
−
[[file:ATTEN1_NanoVNA_40dB_S11_1-100MHz.png]]
 
−
 
 
−
* VSWR
 
−
* 1-900 MHz
 
−
 
 
−
[[file:ATTEN1_NanoVNA_40dB_VSWR_1-100MHz.png]]
 
−
 
 
−
=== DC Block ===
 
−
 
 
−
* Use same PCB
 
−
** Install 0.1uF cap between the two SMAs
 
−
* S21 of -0.8 dB at 50 KHz
 
−
* S21 of 0.44 dB at 900 MHz
 
−
 
 
−
[[FILE:ATTEN1_NanoVNA_DC-BLOCK_S21_50KHz-900MHz.png]]
 
−
 
 
−
*S11
 
−
 
 
−
[[FILE:ATTEN1_NanoVNA_DC-BLOCK_S11_50KHz-900MHz.png]]
 
−
 
 
−
== Attenuator Charts ==
 
−
 
 
−
[[file:dBm_vs_milliVolt_milliWatts.PNG]]
 
−
 
 
−
[[file:dBm_vs_Volta_Watts.PNG]]
 
−
 
 
−
[[file:dBm_vs_Volt_Watts.PNG]]
 
−
 
 
−
== References ==
 
−
 
 
−
* [http://leleivre.com/rf_pipad.html Attenuator Calculator] - Le Leivre.com
 
−
* [https://www.pasternack.com/t-calculator-pi-attn.aspx Attenuator Calculator] - Pasternak
 
−
 
 
−
* Heavily inspired by Alan (W2AEW) video
 
−
 
 
−
<video type="youtube">A5gGeV7CiQ0</video>
 
−
 
 
−
[[file:W2AEW_Attns-01.PNG]]
 
−
 
 
−
[[file:W2AEW_Attns-02.PNG]]
 
−
 
 
−
[[file:W2AEW_Attns-03.PNG]]
 

Revision as of 18:17, 24 October 2021

AudioAmp380-3D.png

Design

  • Pre-amp plus power amp
  • 50 Ohm input impedance
  • Gain trimmer potentiometer on preamp
  • External mount gain potentiometer
  • [1] Pre-amplifier
  • LM380 2.5W Audio Power Amplifier
  • 12V nominal power
    • 10-22V
  • Fits into 80x50x20mm extruded aluminum enclosure

`

Pre-Amplifier (NE5534)

  • Low-Noise Operational Amplifiers
  • Equivalent Input Noise Voltage 3.5 nV/√Hz Typ
  • Unity-Gain Bandwidth 10 MHz Typ
  • Common-Mode Rejection Ratio 100 dB Typ
  • Wide Supply-Voltage Range ±3 V to ±20 V
  • Used as single supply

Audio Power Amplifier (LM380)

  • Wide Supply Voltage Range: 10V-22V
  • Low Quiescent Power Drain: 0.13W (VS= 18V)
  • Voltage Gain Fixed at 50 (34 dB)
  • High Peak Current Capability: 1.3A
  • Input Referenced to GND
  • High Input Impedance: 150kΩ
  • Low Distortion
  • Quiescent Output Voltage is at One-Half of the Supply Voltage

Controls

  • RV1 - trade-off book gain/bandwidth - Tune for best sound
  • RV2 - volume control (after preamp and before LM380 Amp). 1x5 header wire to external pot
  • J1 - Audio In, 50 Ohms input impedance
  • J2 - Audio Out, 8 Ohm speakers
  • J3 - Power, 10V-22VDC

Rev 2 Schematic

AudioAmp380-Schematic.png

Rev 1 Rework

  • Issues
    • Front end opamp has + and - reversed
    • Also hooked up the feedback to the wrong input
  • Replace R1 with jumper
  • Replace C9 with jumper
  • Remove C2
  • 5 Cuts
    • 4 on front
    • 1 on back
  • 5 jumper segments on back
    • 2 nodes

U2-2 3 Rev1 Rev2 Cuts Jumpers.png

  • Jumpers on rear side

AudioAmp380 Back Jumpers.PNG

Videos

ZL2CTM Schematic.PNG

Assembly Sheet

LM380 Rev 1 Assembly Sheet

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