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AN779L 20 WATT HF DRIVER AMPLIFIER

The AN779 driver amplifier provides a power output of 20 watts with a total power gain of 25 dB and the construction technique allows the use of inexpensive components throughout. The plastic RF power transistors, MRF475 and MRF476, featured in this amplifier, were initially developed for the CB market. The TO-220 packaged parts are ideal for applications up to 50 MHz, where low cost is an important factor. The MRF476 is specified as a 3-watt device and the MRF475 has an output power of 12 watts. Both are extremely tolerant to overdrive and load mismatches, even under CW conditions. Typical IMD numbers are better then -35 dB, and power gains are 18 dB and 12 dB, respectively, at 30 MHz. This amplifier was designed to serve as a 1.6 to 30 MHz broadband driver.

SPECIFICATIONS:wpe18.jpg (16995 bytes)
Frequency Range 1.6 to 30 MHz
RF Power Gain 25 dB (typical)
RF Power Input 100 Milliwatts
RF Power Output 20 Watts
DC Input Voltage 12.5 Volts
DC Input Current 5 amps (typical)

 

 

 

              wpe1A.jpg (16853 bytes)

 

R1, R4 - 10 Ohms, 1/4W C1 - 39 pF dipped Mica RFC5 - Ferroxcube VK200 19/4B
R2, R3 - 30 Ohms, 1/4 W C2, C3 - 680 pF Ceramic Disc RFC1, 2, 3, 4 - 10 uH Molded Choke
R5, R6 - 82 Ohms, 3 W (Nom.) C4, C10 - 220 uF, 4 V, Tantalum B - Ferrite Beads (Ferroxcube #56 590 65/3B
R7 - 47 Ohms, 1/4 W C5, C7, C11, C13 - 0.1 uF Ceramic Disc D1, D2 - 1N4001
R8, R11 - 6.8 Ohms, 1/4 W C6 - 56 pF Dipped Mica Q1, Q2 - MRF476
R9, R10 - 15 Ohms, 1/4 W C8, C9 - 1200 pF Ceramic Disc Q3, Q4 - MRF475
R12 - 130 Ohms, 1/4 W C12, C14 - 10 uF, 25 V Tantalum T1, T2 - 4:1 Impedance Transformer
    T3 - 1:4 Impedance Transformer

Printed Circuit Boards and Components Available

The above is a summary description of an HF amplifier described in the MOTOROLA Engineering Bulletins and Application Notes. These Engineering Bulletins and Application Notes may be obtained from your local MOTOROLA office or can be found in the MOTOROLA RF DEVICE DATA MANUAL. These amplifiers have been designed and tested by engineers at Motorola.

 

COMPONENT SETS FOR AN779L

 
Capacitor Set

$ 11.50
1 ea. 39pf Silver Dipped Mica Cap.
1 ea. 56pf Silver Dipped Mica Cap.
2 ea. 680pf Ceramic Disc Cap.
2 ea. 1200pf Ceramic Disc Cap.
4 ea. 0.1uf Ceramic Disc Cap.
2 ea. 10uf 25 V Tantalum Cap.
2 ea. 220uf 4 V Tantalum Cap.

 
Resistor Set

$ 1.75
2 ea. 6.8 ohm 1/4 W Resistor
2 ea. 10 ohm 1/4 W Resistor
2 ea. 15 ohm 1/4 W Resistor
2 ea. 30 ohm 1/4 W Resistor
1 ea. 47 ohm 1/4 W Resistor
1 ea. 130 ohm 1/4 W Resistor
2 ea. 75 ohm 3 W Resistor

 
Semiconductor Set

$ 50.50
2 ea. 1N4001 Diode
2 ea. MRF475 Matched RF Transistors
2 ea. MRF476 Matched RF Transistors

 
Ferrite Set

$ 6.25
1 ea. VK200/20/4B Ferroxcube Choke
4 ea. 10 uh Molded Choke
8 ea. 56-590-65/3B Ferrite Beads

 
Transformer Set

$ 11.75
1 ea. T1 Input Transformer (wound)
1 ea. T2 Interstage Transformer (wound)
1 ea. T3 Output Transformer (wound)

 
Miscellaneous Hardware Set

$ 3.75
4 ea. 1/8 inch spacers
2 ea. Transistor Heat Sinks #6106
4 ea. 4-40x3/8 Screw with Nut

 

Printed Circuit Board (2 9/16"W x 5"L)

$ 17.50

 

 Send mail to cci.dayton@pobox.com with questions or comments about this web site.           

 

                This Page was last updated April 18, 2007