Download: APPLICATION NOTE A wide-band class-A linear power amplifier (174 − 230 MHz) with 2 transistors BLV33F ECO8005

APPLICATION NOTE A wide-band class-A linear power amplifier (174 − 230 MHz) with 2 transistors BLV33F ECO8005,

CONTENTS

1 ABSTRACT 2 INTRODUCTION 3 DESIGN OF THE AMPLIFIER 4 ADJUSTMENTS OF THE AMPLIFIER 5 ASSEMBLING OF THE AMPLIFIER AND MECHANICAL DATA 6 MEASURED RESULTS 7 CONCLUSION 8 REFERENCES 1998 Mar 23 2, 1 ABSTRACT For application in driver or final stages of TV-transposers in Band III (174-230 MHz) a linear wideband power amplifier has been designed with 2 transistors BLV33F, coupled by means of 3 dB − 90° hybrids. Each transistor is adjusted in Class-A at VCE = 25 V and IC = 3.25 A. A demonstration model showed a peak sync. output power of 40 W at a 3-tone I.M. distortion between −52 and −53 dB. At this power level the cross-modulation varied from 15 to 18%. The power gain is between 13.3 and 13.6 dB. For natural convection cooling the heatsink temperature is 40 °C above ambient temperature. 2 INTRODUCTION For application in T.V. transposers and transmitters for Band III a wideband linear power amplifier has been designed with 2 transistors BLV33F, coupled by means of 3 dB −90° hybrids. Each transistor is adjusted in Class-A at VCE = 25 V and IC = 3.25 A. Note: The BLV33F is a high gain, internally matched, 1/2 inch 6 leads flange version of the BLV33. 3 DESIGN OF THE AMPLIFIER For class-A operation the BLV33F is specified at VCE = 25 V, IC = 3.25 A. The corresponding typical gain, input and load impedance are given in Table 1: Table 1 FREQ. GAIN INPUT IMPEDANCE LOAD IMPEDANCE (MHz) (dB) (Ω) (Ω) 174 12.94 0.85 + j0.59 2.68 + j1.24 202 12.88 1.02 + j0.47 2.23 + j0.90 230 13.91 0.93 + j0.02 1.84 + j0.51 To obtain a high linear output and at the same time good input and output matching (V.S.W.R. ≤1.2) 3 dB −90° hybrids are used. The reflected input power will be absorbed in the 50 Ω resistor, matching the isolated port (see Fig.1). For detailed information on computer-aided design (carried out by Mr. Hilbers Central Application Laboratory) see Refs 1, 2 and 3. The transistors used in this particular amplifier are typical products, measured in a narrow band test amplifier and specified as follows: VCE = 25 V − IC = 3.25 A − Th = 70° Table 2 Transistor type BLV33F Batch no. MD 8-16 no.7 MD 8-16 no. 10 Vision frequency 224.25 MHz Output power (peak sync) 17.7 W 18 W Intermod. product −55 dB −55 dB Gain 14.2 dB 14.2 dB 4 ADJUSTMENTS OF THE AMPLIFIER The amplifier consists of two equal BLV33F branches (see Fig.1) and both transistors are separately biased at VCE = 25 V − IC = 3.25 A. The printed circuit board of the 2× BLV33F wideband amplifier is given in Fig.2 and schematic diagram + lay-out of the bias unit is given in Fig.3. Figure 9 at the end of the report shows the lay-out of the amplifier with 1998 Mar 23 3, the situation of the components. Each branch was adjusted for maximum and flat gain by means of a high power sweep with a frequency range from 170 − 230 MHz. The output of the amplifier was levelled at 40 W which means about 50% of the D.C. input power. After that, both branches are coupled by means of 3 dB −90° hybrids. 5 ASSEMBLING OF THE AMPLIFIER AND MECHANICAL DATA Due to the dimensions of the printed circuit board (220 × 210 mm) 2 extruded blackened aluminium heat sinks (cat.no. 56293) are screwed on an aluminium plate (thickness 12 mm) which on its turn is screwed on the heat sink. Special attention has been paid to the surface finishing to keep the thermal resistance as low as possible. Dimensions of the amplifier: l = 224 mm − w = 223 mm − h = 113 mm. Weight: 7.5 kg. 6 MEASURED RESULTS In Fig.4 the typical results of crossmodulation and 3-tone intermod. product (from 170 − 230 MHz) have been given for peak sync output powers of 30 W and 40 W. Figure 5 shows peak sync output power as function of 3-tone intermod. products (measured on channel 12: Vision freq. 224.25 MHz − Sound freq. 229.75 MHz). In Figs 6 and 7 the forward and reverse transducer gain as well as input and output voltage standing wave ratio are given. The measuring test set-up is depicted in Fig.8. Note: Signal levels 3-tone measurements: Vision carrier −8 dB; Sound carrier −7 dB; Sideband −16 dB; 0 dB corresponds to peak sync. Signals levels crossmodulation: Vision carrier switched from −20 dB to 0 dB; Sound carrier −7 dB; 0 dB = peak sync level Crossmodulation is defined as the voltage variation (%) of the sound carrier. 7 CONCLUSION Two transistors BLV33F, coupled by means of 3 dB −90° hybrids, can deliver an output power (peak sync) of typ. 40 W for −52 dB 3-tone intermodulation. At 40 W output the crossmodulation varied from 15% to 18% in Band III (170 − 230 MHz). The gain of the amplifier is typically 13.3 + 0.3 dB. The required D.C. input is approx. 165 W. Using a high power sweep with adjustable transistor output levelling provides a suitable method to adjust a linear wideband power amplifier. 8 REFERENCES Ref.1: G.L. Matthaei − Tables of Chebyshev Impedance Transforming Network of Low-Pass Filter Form. Proceedings of the IEEE August 1964, pp 939 − 963. Ref.2: A.H. Hilbers and M.J. Köppen − A wideband linear power amplifier (470 − 860 MHz) with two transistors BLW34. C.A.B. report ECO7901. Ref.3: R.F.F. Zwanen − A wideband Class-A linear power amplifier (170 − 230 MHz) with two transistors BLV33. C.A.B. report ECO7904. 1998 Mar 23 4, ook, full pagewidth 1998 Mar 23 5 This text is here in white to force landscape pages to be rotated correctly when browsing through the pdf in the Acrobat reader.This text is here in _white to force landscape pages to be rotated correctly when browsing through the pdf in the Acrobat reader.This text is here inThis text is here in white to force landscape pages to be rotated correctly when browsing through the pdf in the Acrobat reader. white to force landscape pages to be ... Vb Vc C25 R3 C19 C26 C13 C27 L3 L11 C3 C7 C14 C21 C31 L7 C1 L4 L9 L13 L15 L19 L1 L17 L21 BLV33F C4 C8C11C15 C22C32 C35 R5 R6 R.F. input 50 Ω in 0° −90° iso H1 H2 R.F. output iso −90° 0° in 50 Ω R1 R2 C5 C9 C12 C16 C23 C34 C36 L8L5 L10L14L16 L20C2 L2 L18 L22BLV33F C6 C10 C17 C24C33 L12 L6 C28 C18 C29 R4 C20 C30 Vb Vc MGP959 Fig.1 2× BLV33F Band III Class A linear power amplifier., handbook, full pagewidth MGP986 Fig.2 Printed circuit board 2× BLV33F wideband power amplifier. 1998 Mar 23 6, Table 3 Parts list: BLV33F Band III Class A linear power amplifier (170 − 230 MHz) C1 = C2 = C7 = C9 10 pF chip capacitor C3 = C6 = C32 = C34 1.8 to 10 pF film dielectric trimmer (cat. no. 222280905002) C4 = C5 = C35 = C36 220 pF chip capacitor C8 = C10 39 pF chip capacitor C11 = C12 68 pF chip capacitor C13 = C18 = C27 = C28 1000 pF chip capacitor C14 = C15 = C16 = C17 120 pF chip capacitor C19 = C20 = C26 = C29 300 nF metallized film capacitor (cat. no. 222235225334) C21 = C22 = C23 = C24 56 pF chip capacitor C25 = C30 10 µF (40 V) electrolytic capacitor (cat. no. 222212117109) C31 = C33 18 pF chip capacitor (chip capacitors: ATC type 100B − C − MSX − 500) R1 = R2 = R5 = R6 100 Ω power metal film resistor PR52 type (cat. no. 232219231001) R3 = R4 10 Ω carbon resistor CR68 type H1 = H2 3 dB −90° coupler, model no. 10262 − 3, range 125 to 250 MHz, ANAREN MICROWAVE INC. L1 = L2 25 nH 2 turns enamelled Cu wire (1 mm); int. diam. 5 mm; leads 2 × 3 mm L3 = L6 90 nH 5 turns closely wound enamelled Cu wire (1.5 mm) int. diam. 6.5 mm; length 5 mm; leads 2 × 9 mm L4 = L5 60 Ω stripline; w = 2 mm; length = 30 mm L7 = L8 30 Ω stripline; w = 6 mm; length = 11 mm L9 = L10 40 Ω stripline; w = 4 mm; length = 5 mm L11 = L12 20 nH Cu strip (1 mm); length = 17 mm; h = 5 mm; w = 4 mm L13 = L14 30 Ω stripline; w = 6 mm; length = 17 mm L15 = L16 30 Ω stripline; w = 6 mm; length = 4 mm L17 = L18 28 nH 2 turns enamelled Cu wire (1.5 mm); int. diam. 6.5 mm; length 9 mm; leads 2 × 3 mm L19 = L20 30 Ω stripline; w = 6 mm; length = 6 mm L21 = L22 50 Ω stripline; w = 3 mm; length = 15 mm The striplines are printed on double Cu-clad printed circuit board with epoxy fibre-glass dielectric (εr = 4.5); thickness 1/16 inch. 1998 Mar 23 7, Table 4 Parts list: Class A bias circuit for a single transistor BLV33F R1 150 Ω carbon resistor CR25 type R2 100 Ω preset potentiometer CTP10 type R3 10 Ω carbon resistor CR25 type R4 1000 Ω carbon resistor CR25 type R5 = R6 = R7 1.8 Ω rectangular wirewound resistor EH707 type R8 = R9 180 Ω carbon resistor CR25 type R10 33 Ω carbon resistor CR25 type C1 = C3 100 nF metallized film capacitor C2 100 pF ceramic capacitor C4 10 µF electrolytic capacitor D1 BZY 88 (3V3) D2 BY 206 T1 BD 136 1998 Mar 23 8, handbook, full pagewidth Vs (+ 27 V) R5 R6 D2 e R7 b C4 TR1 BD136 R1 c Vc Vce = 25 V C1 C2 D1 C3 R2

V

R3 bR8 R9 BLV33F R4 R10 MGP983 handbook, full pagewidth 55 R5 C1 C2 R6 R7 C4 Vs D2 Vc C3 72 e R2 c R1 b D1 R8 Vb R3 R9 R4 R10 MGP984 Fig.3 Class A bias circuit for a single transistor BLV33F. 1998 Mar 23 9, MGP960 handbook, full pagewidth crossmod. (%) 40 W Po sync 30W0dB 0 dB = Po sync −7 dB ∆V (%) −20 dB 168 175 182 189 196 203 210 217 f (MHz) 224 MGP961 −44 handbook, full pagewidth intermod. 0 dB = Po sync product −8 dB −7 dB(dB) intermod. −16 dB product −48 Po sync −52 40 W −56 30 W −60 −64 168 175 182 189 196 203 210 217 f (MHz) 224 2× BLV33F Class A linear power amplifier. VCE − 25 V − IC = 2 × 3.25 A − Tamb − 23 °C − Th = 65 °C. Fig.4 Crossmodulation and intermodulation products of the 2× BLV33F wideband Band III linear power amplifier. 1998 Mar 23 10, − MGP96245 handbook, full pagewidth intermod. product (dB) −50 −55 −60 Po sync −8 dB −7 dB −16 dB − intermod.65 product 224.25 MHz 229.75 MHz −70 0 20 40 60 80 100 120 140 Po sync (W) 2× BLV33F Band III amplifier. VCE = 25 V; IC = 2 × 3.25 A; Tamb = 23 °C; Th = 65 °C. Fig.5 3-tone intermodulation product as function of Po sync. Vision freq. 224 MHz; sound freq 229.5 MHz. 1998 Mar 23 11, MGP963 handbook, halfpage (dB) S21 150 170 190 210 230 250 (MHz) a. Forward transducer gain. MGP964 handbook, halfpage (dB) 0 V.S.W.R. −10 2 1.5 −20 1.2 1.1 −30 −40 S11 150 170 190 210 230 250 (MHz) b. Input voltage standing wave ratio. Fig.6 2× BLV33F wideband Band III power amplifier. 1998 Mar 23 12, MGP965 −20 handbook, halfpage (dB) −25 −30 −35 150 170 190 210 230 250 (MHz) a. Reverse transducer gain. MGP966 handbook, halfpage (dB) 0 V.S.W.R. −10 2 1.5 −20 1.2 1.1 −30 −40 S22 −50 150 170 190 210 230 250 (MHz) b. Output voltage standing wave ratio. Fig.7 2× BLV33F wideband power amplifier. 1998 Mar 23 13, andbook, full pagewidth 1998 Mar 23 14 This text is here in white to force landscape pages to be rotated correctly when browsing through the pdf in the Acrobat reader.This text is here in _white to force landscape pages to be rotated correctly when browsing through the pdf in the Acrobat reader.This text is here inThis text is here in white to force landscape pages to be rotated correctly when browsing through the pdf in the Acrobat reader. white to force landscape pages to be ...

COAX

50 Ω SWITCH 8554L HP435A SPECTRUM WATT ANALYZER METER POWER POWER DIVIDER BAND III DIVIDER 20 20ATT. ATT. WIDEBAND dB dB 50 Ω POWER AMPLIFIER 50 Ω 50 Ω 50Ω3dB - 180° D.U.T. × ATT. (100W) ATT.

HYBRID

BLV33F 10 6 COAX COAX HP778D HP778DSWITCH SWITCH dB dB CD ATT. DIRECT. COUPLER DIRECT. COUPLER 50-450 Ω 10 dB

ALC

CIRCULATOR RANGES: 170 to 200 MHz 6 VAR. VAR.190 to 230 MHz dB ATT. ATT. BLV33 10 S.M.L.U. AMPLIFIER dB R.F. GEN. COAX 50 Ω 50 Ω 50 Ω DETECTOR VAR. ATT. BLV33 10 S.M.L.U. 20 dB AMPLIFIER dB R.F. GEN. SWOB III PM5171 D.C. AMPLIFIER 50 Ω 50 Ω 50 Ω 50 Ω 50 Ω VAR. SWEEP ALC ATT. S.M.L.U. S.M.L.U. BLV33 BLV33 10 S.M.L.U. SWEEP R.F. GEN. AMPLIFIER AMPLIFIER dB R.F. GEN. 50 Ω 50 Ω 50 Ω POWER SWEEP TEST SET-UP 170 to 230 MHz 3-TONE TEST SET-UP MGP985 Fig.8 Test set up 2× BLV33F Band III power amplifier., Unfortunately the numbers in the lay-out of Fig.9 do not correspond with those of the schematic diagram of Fig.1. The reader is referred to the translation Table 5. Table 5 NUMBER IN LAY-OUT (see Fig.9) NUMBER OF SCHEMATIC DIAGRAM (see Fig.1) R1 R3 R2 R5 R3 R6 C2 C1 C3 C3 C4 C4 C5 C7 C6 C8 C7 C11 C8 C14 C9 C15 C10 C19 C11 C13 C12 C21 C13 C22 C14 C25 C15 C26 C16 C27 C17 C31 C18 C32 C19 C35 L1 L1 L3 L3 L6 L11 L9 L17 1998 Mar 23 15, handbook, full pagewidth Vb Vc R1 C14 C10 C15 C11 C8 C16 L3 L6 C12 L9 C17 C6 C5 C7 C13 L1 C3 C18 C6 C9 BLV33F R2 R3 C19 50 Ω C4IN input HYBRID HYBRID COUPLER COUPLER 50 Ω IN output MGP987 Vb Vc Fig.9 Lay-out of amplifier with situation of components. 1998 Mar 23 16,

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