1 description ltc 6431-20 50 20db gain block if amplifier demonstration circuit 2077 a features the lt c ? 6431-20 50 gain block if amplifier. the LTC6431-20 has a power gain of 20.8 db and it is part of the ltc6431-yy amplifier series. the dc2077a demo board supports the ltc6431- yy am - plifier family . the dc2077a demo board is optimized for a frequency range from 100 mhz to 1200 mhz. it incorpo- rates a minimum of passive components to configure the l , lt, ltc, ltm, linear technology and the linear logo are registered trademarks of linear technology corporation. all other trademarks are the property of their respective owners. block diagram amplifier for various applications. the LTC6431-20 pro- vides 50 single-ended input and output impedances so that it can be easily evaluated with most rf test equipment. design files for this circuit board are available at http://www .linear.com/demo figure 1. LTC6431-20 device block diagram 24 18 16 20db gain bias and temperature compensation v cc 9, 22 out in gnd 8, 17, 23, 25 (exposed pad) t_diode 643122 bd dc2077af demo manual dc2077a
2 performance summary operation table 1. typical demo board performance summary symbol parameter conditions value / unit power supply v cc operating supply range all v cc pins plus out 4.75v to 5.25v i cc current consumption total current 95ma t a = 25c, v cc = 5v frequency (mhz) power gain |s21| output third-order intercept point 1 oip3 output third-order intermodu- la tion 1 oim3 second harmonic distor tion 2 hd2 third harmonic distortion 2 hd3 output 1db compression point p1db noise figure 3 nf 100 20.2 47.2 C90.4 C56.8 C96.7 23.2 3.2 200 20.6 48.0 C91.9 C55.6 C92.9 22.4 2.7 240 20.6 47.9 C91.9 C52.5 C106.1 22.0 2.7 300 20.7 47.9 C91.9 C50.5 C83.1 21.8 2.8 400 20.6 46.9 C89.9 C50.4 C77.4 21.7 2.8 500 20.6 45.0 C86.0 C47.8 C72.6 21.8 2.9 600 20.6 42.5 C81.0 C43.7 C64.0 21.7 3.1 700 20.5 39.7 C75.5 C42.1 C60.7 21.4 3.3 800 20.5 38.6 C73.1 C40.6 C63.1 21.4 3.4 900 20.5 37.1 C70.3 C37.1 C60.4 21.1 3.7 1000 20.4 36.0 C68.0 C36.9 C55.1 20.8 3.8 1100 20.3 35.1 C66.2 C35.7 C54.5 20.4 3.9 1200 20.2 34.4 C64.8 C34.4 C53.6 20.3 4.1 units db dbm dbc dbc dbc dbm db notes: all figures are referenced to j1 (input port) and j2 (output port). 1. tw o - tone test conditions: output power level = +2dbm/tone, tone spacing = 1mhz. 2. single-tone test conditions: output power level = +6dbm. 3. small-signal noise figure. the demo circuit 2077 a is a high linearity, fixed gain amplifier. it is designed for ease of use. both the input and output are internally matched to 50 single-ended source and load impedance. figure 2 shows the dc2077 as s-parameters. figure 4 shows the demo circuit s schematic. the input and output dc blocking capacitors ( c1 and c7) are required because this device is internally dc biased for optimal operation. the frequency appropriate choke ( l1) and the decoupling capacitors ( c3 and c4) provide the proper dc bias to the rf output node. only a single 5 v supply is necessary for the vcc pins on the device. l 2 and c 6 are optional parts. these additional components allow for further optimization to lower or wider frequency range applications. a parallel 62pf ( c2) and 348 ( r1) input network has been added to ensure low frequency stability. note that the input stability network does degrade performance below 150mhz. low frequency performance can be improved by increasing the value of capacitor c2. the t_diode pin ( turret e1) can be forward biased to ground with 1 ma of current. the measured voltage will be an indicator of the chip junction temperature (t j ). dc2077af demo manual dc2077a
3 operation please note that a number of dnc pins are connected on the demo board. these connections are not necessary for normal operation. failure to float these pins may impair the operation of the device. table 2 shows the function of each input and output on the board. table 2. dc2077a board i/o descriptons connector function j1 (in) single-ended input. impedance matched to 50. drive from a 50 network analyzer or signal source. j2 (out) single-ended output. impedance matched to 50. drives a 50 network analyzer or spectrum analyzer. e1 (t_diode) the measured voltage will be an indicator of the chip junction temperature. e2 (vcc) positive supply voltage source. e3 (gnd) supply ground. additional information as with any rf device, minimizing ground inductance is critical. care should be taken during the board layout when using these exposed pad packages. the maximum number of small-diameter vias should be placed underneath the exposed pad. this will ensure a good rf ground and low thermal impedance. maximizing the copper ground plane will also improve heat spreading and lower the inductance to ground. it is a good idea to cover the via holes with solder mask on the back side of the pcb to prevent solder from wicking away from the critical pcb to exposed pad interface. the dc2077a is a wide bandwidth demo board, but it is not intended for operation down to dc. the lower frequency cutoff is limited by on-chip matching elements. frequency (mhz) 0 |s21| (db) |s11|, |s12|, |s22| (db) 16 20 24 nominal working frequency range 1600 12 8 14 18 22 10 6 4 ?12 ?4 4 ?20 ?28 ?16 ?8 0 ?24 ?32 ?36 400 800 1200 2000 |s21| |s22| |s11| |s12| figure 2. demo board s-parameters table 3 shows the ltc643x- yy amplifier series and its associated demo boards. each demo board lists the typical working frequency range and the input and output imped - ance of the amplifiers. setup signal sources and spectrum analyzer the LTC6431-20 is an amplifier with high linearity perfor - mance. therefore, the o utput intermodulation products are very low. even using high dynamic range test equipment, third-order intercept ( ip3) measurements can drive test setups to their limits. consequently, accurate measure - ment of ip3 for a low distortion ic such as the LTC6431-20 requires certain precautions to be observed in the test setup as well as the testing procedure. table 3. the ltc643x- yy amplifier family and corresponding application demo boards demo board number frequency range (mhz) notes/applications boards in/out impedance amplifier amplifiers impedance dc1774a-a 50 to 350 low frequency 50 ltc6430-15 differential 100 dc1774a-b 400 to 1000 mid frequency 50 ltc6430-15 differential 100 dc1774a-c 100 to 1200 wide frequency 50 ltc6431-15 single-ended 50 dc2032a 50 to 1000 cable infrastructure 75 ltc6430-15 differential 100 dc2077a 100 to 1200 wide frequency 50 LTC6431-20 single-ended 50 dc2153a 700 to 1700 high frequency 50 ltc6430-15 differential 100 dc2077af demo manual dc2077a
4 operation setup signal sources figure 4 shows a proposed ip3 test setup. this setup has low phase noise, good reverse isolation, high dynamic range, sufficient harmonic filtering and wideband imped - ance matching. the setup is outlined below: a . hi gh performance signal generators 1 and 2 ( hp8644 a) are used. these suggested generators have low har - monic distortion and very low phase noise. b. high linearity amplifiers are used to improve the reverse isolation. this prevents crosstalk between the two signal generators and provides higher output power. c. a lowpass filter is used to suppress the harmonic content from interfering with the test signal. note that second order inputs can mix with the fundamental frequency to form intermodulation ( im) products of their own. we suggest filtering the harmonics to -50dbc or better. d. the signal combiner from mini- circuits ( adp-2-9) combines the two isolated input signals. this combiner has a typical isolation of 27 db. for improved vswr and isolation, the h-9 signal combiner from ma/com is an alternative which features >40 db isolation and a wider frequency range. passive devices ( e.g. combiners) with magnetic elements can contribute nonlinearity to the signal chain and should be used cautiously. e. the attenuator pads on all three ports of the signal combiner will further support isolation of the two input signal sources. they also reduce reflections and promote maximum power transfer with wideband impedance matching. setup the spectrum analyzer a. adjust the spectrum analyzer for maximum possible resolution of the intermodulation products amplitude in dbc. a narrower resolution bandwidth will take a longer time to sweep. b. optimize the dynamic range of the spectrum analyzer by adjusting the input attenuation. first increase the spectrum analyzer s input attenuation ( normally in steps of 5 db or 10 db). if the im product levels decrease when the input attenuation is increased, then the input power level is too high for the spectrum analyzer to make a valid measurement. most likely, the spectrum analyzers 1 st mixer was overloaded and producing its own im products. if the im reading holds constant with increased input attenuation, then a sufficient amount of attenuation was present. adding too much attenua - tion will bury the intended im signal in the noise floor. therefore, select just enough attenuation to achieve a stable and valid measurement. c. in order to achieve this valid measurement result, the test system must have lower total distortion than the duts intermodulation. for example , to measure a 48dbm oip3, the measured intermodulation products will be C92 dbc below the C18 dbm per tone input level and the test system must have intermodulation products approximately C98 dbc or better. for best results, the im products and noise floor should measure at least C102dbc before connecting the dut. dc2077af demo manual dc2077a
5 quick start procedure demo circuit 2077 a can be set up to evaluate the perfor- mance of the LTC6431-20. refer to figure 3 for proper equipment connections and follow the procedure below: tw o -tone measurement connect all test equipment as suggested in figure 3. 1. the power labels of vcc 4.75 v-5.25v and gnd directly correspond to the power supply. typical current con - sumption of the LTC6431-20 is about 95ma. 2. apply two independent signals f1 and f2 from signal generator 1 and signal generator 2 at 240 mhz and 241mhz, while setting the amplitude to C18dbm/tone at the demo board input (j1). 3. monitor the output tone level on the spectrum analyzer. adjust the signal generator levels such that the output power measures +2dbm/ tone at the amplifier output j 2, after correcting for external cable losses and attenuations. 4. change the spectrum analyzers center frequency and observe the two im3 tones at 1 mhz below and above the input frequencies. the frequencies of im3_low and im3_high are 239 mhz and 242 mhz, respectively. the measurement levels should be approximately C92dbc; +48dbm is typical oip3 performance for the ltc6431 - 20 at 240mhz. the oip3 calculation is: oip3 = pout + ?imd3/2 where: pout is the lower output signal power of the funda- mental products. ? imd3 = pout C pim3; pim3 is the higher third-order intermodulation product. single-tone measurement 5. continue with step 4 above, turn off one signal source to measure gain and harmonic distortions. combiner mini-circuits adp-2-9 signal generator 1 hp8644a hp8644a lowpass filter lowpass filter vcc = 4.75v to 5.25v 6db attn pad (optional) 6db attn pad (optional) 3db attenuation pad 20db attenuation pad coaxial cable spectrum analyzer rohde & schwarz fsem30 amplifier mini-circuits zhl-2 or equivalent amplifier mini-circuits zhl-2 or equivalent signal generator 2 dc power supply gnd v + figure 3. proper equipement setup for ip3 measurement dc2077af demo manual dc2077a
6 parts list item qty reference part description manufacturer/ part number 1 3 c1, c3, c7 cap., x7r, 1000pf, 50v 5%, 0603 avx , 06035c102 jat 2a 2 1 c2 cap., npo, 62pf, 25v, 5%, 0402 avx , 04023a620 jat 3 1 c4 cap., x5r, 0.1f, 10v, 10%, 0603 avx , 0603zd104 kat 2a 4 2 c5, c8 cap., x7r, 1000pf, 50v 5%, 0402 avx , 04025c102 jat 2a 5 1 c6 cap., opt , 0603 6 3 e1-e3 testpoint, turret, 0.093" mill-max, 2501-2-00-80-00-00-07-0 7 2 j1-j2 conn., sma 50 edge-launch e.f.johnson, 142-0701-851 8 1 l1 inductor, chip, 560nh, 5%, 0603ls-1608 coilcraft, 0603ls-561xjlb 9 1 l2 res., chip, 0, 0603 vishay, crcw06030000z0ed 10 1 r1 res., chip, 348, 1%, 1/16w, 0402 vishay,crcw0402348rfked 11 0 r3 res., opt , 0402 12 1 u1 balanced amplifier ltc6431aiuf-20, qfn24uf-4x4 linear tech., ltc6431aiuf-20 dc2077af demo manual dc2077a
7 information furnished by linear technology corporation is believed to be accurate and reliable. however, no responsibility is assumed for its use. linear technology corporation makes no representa- tion that the interconnection of its circuits as described herein will not infringe on existing patent rights. figure 4. dc2077a demo board schematic schematic diagram 5 5 4 4 3 3 2 2 1 1 d d c c b b a a ???????????????????????????????????? ????????????????????????????? ???????????????????????????????? ??????????????? ?????????????????????????????????????????????? ????? ???? ???? ??? ??? ??? ??? ???????????????? ??????????? ???? ???????? ??? ??? ??????? ????????? ? ???????? ?? ???????????????? ??????????? ???? ???????? ??? ??? ??????? ????????? ? ???????? ?? ???????????????? ??????????? ???? ???????? ??? ??? ??????? ????????? ? ???????? ?? ???? ????? ?????? ???? ????? ?? ?????? ????????? ???????? ???????? technology ?????????????????? ?????????????????? ???????????????????? ??????????????????? ?????????????????????????????????????? ??????????????? ???????????????????????????????????????????????????? ???????????????????????????????????????????????????? ???????????????????????????????????????????????????? ?????????????????????????????????????????????????? ???????????????????????????????????????????????? ????????????????????????????????????????????????????? ??????????????????????????????????????????? ??????????????????????????????????????????????????? ???????????????????????????????????????????????????? ????????? ?????????????????????????????????????????????? ???????????? ?????????????? ? ???????????????????????? ?? ?????????????????? ??? ??????? ??? ?????????? ?????????????????? ???? ????? ?????? ???? ????? ?? ?????? ????????? ???????? ???????? technology ?????????????????? ?????????????????? ???????????????????? ??????????????????? ?????????????????????????????????????? ??????????????? ???????????????????????????????????????????????????? ???????????????????????????????????????????????????? ???????????????????????????????????????????????????? ?????????????????????????????????????????????????? ???????????????????????????????????????????????? ????????????????????????????????????????????????????? ??????????????????????????????????????????? ??????????????????????????????????????????????????? ???????????????????????????????????????????????????? ????????? ?????????????????????????????????????????????? ???????????? ?????????????? ? ???????????????????????? ?? ?????????????????? ??? ??????? ??? ?????????? ?????????????????? ???? ????? ?????? ???? ????? ?? ?????? ????????? ???????? ???????? technology ?????????????????? ?????????????????? ???????????????????? ??????????????????? ?????????????????????????????????????? ??????????????? ???????????????????????????????????????????????????? ???????????????????????????????????????????????????? ???????????????????????????????????????????????????? ?????????????????????????????????????????????????? ???????????????????????????????????????????????? ????????????????????????????????????????????????????? ??????????????????????????????????????????? ??????????????????????????????????????????????????? ???????????????????????????????????????????????????? ????????? ?????????????????????????????????????????????? ???????????? ?????????????? ? ???????????????????????? ?? ?????????????????? ??? ??????? ??? ?????????? ?????????????????? ?? ??? ?? ??? ??? ??? ?? ?? ?? ?????? ???? ?? ?????? ???? ?? ????? ???? ?? ????? ???? ?? ??? ?? ??? ?? ??? ?? ??? ?? ?? ?? ? ?? ? ??? ??? ?? ?? ?? ?????? ?? ?????? ?? ??????? ?? ??????? ??? ??? ?? ?? ??? ??? ?? ?????????? ?? ?????????? ??? ? ??? ?? ??? ? ?? ?? ??? ? ??? ? ??? ? ??? ?? ??? ?? ??? ?? ??? ?? ??? ?? ??? ?? ??? ?? ??????? ?? ??? ? ??? ? ??? ? ??? ?? ??? ?? ??? ?? ??? ?? ??? ? ??? ?? ??? ?? ??? ??? ?? ?? ?? ?? ?? ?????? ?? ?????? ??? ??? ?? ????? ?? ????? ?? ?? ?? ??? ?? ??? ?? ???? ?? ???? ?? ?????? ???? ?? ?????? ???? ?? ??? ?? ??? ?? ?? ?? ??? ?? ??? ?? ?????? ???? ?? ?????? ???? dc2077af demo manual dc2077a
8 linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 fax : (408) 434-0507 www.linear.com ? linear technology corporation 2014 lt 0314 ? printed in usa demonstration board important notice linear technology corporation ( lt c ) provides the enclosed product(s) under the following as is conditions: this demonstration board ( demo board) kit being sold or provided by linear technology is intended for use for engineering development or evaluation purposes only and is not provided by lt c for commercial use. as such, the demo board herein may not be complete in terms of required design-, marketing-, and/or manufacturing-related protective considerations, including but not limited to product safety measures typically found in finished commercial goods. as a prototype, this product does not fall within the scope of the european union directive on electromagnetic compatibility and therefore may or may not meet the technical requirements of the directive, or other regulations. if this evaluation kit does not meet the specifications recited in the demo board manual the kit may be returned within 30 days from the date of delivery for a full refund. the foregoing warranty is the exclusive warranty made by the seller to buyer and is in lieu of all other warranties, expressed, implied, or statutory, including any warranty of merchantability or fitness for any particular purpose. except to the extent of this indemnity, neither p arty shall be liable to the other for any indirect, special, incidental, or consequential damages. the user assumes all responsibility and liability for proper and safe handling of the goods. further, the user releases lt c from all claims arising from the handling or use of the goods. due to the open construction of the product, it is the users responsibility to take any and all appropriate precautions with regard to electrostatic discharge. also be aware that the products herein may not be regulatory compliant or agency certified (fcc, ul, ce, etc.). no license is granted under any patent right or other intellectual property whatsoever. lt c assumes no liability for applications assistance, customer product design, software performance, or infringement of patents or any other intellectual property rights of any kind. lt c currently services a variety of customers for products around the world, and therefore this transaction is not exclusive. please read the demo board manual prior to handling the product . persons handling this product must have electronics training and observe good laboratory practice standards. common sense is encouraged. this notice contains important safety information about temperatures and voltages. for further safety concerns, please contact a lt c applica- tion engineer. mailing address: linear technology 1630 mccarthy blvd. milpitas, ca 95035 copyright ? 2004, linear technology corporation dc2077af demo manual dc2077a
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