DEM-OPA26xxE EVALUATION FIXTURE ® DESCRIPTION The DEM-OPA26xxE evaluation board is an unpopulated PCB for dual, wideband op amps in MSOP-8 packages. It supports Burr-Brown’s OPA2650E, OPA2658E and future MSOP-8 dual op amps. Figure 1 shows the pinout that this PCB supports. For more information on component selection for a particular dual op amp, and good PCB layout techniques, see the op amp’s data sheet. The ordering number for this board is MKT-349. Limit of 5 per customer. MEASUREMENT TIPS This evaluation board, and the component values shown, are designed to operate in a 50Ω environment. Most data sheet plots are obtained this way. It is easy to change the component values for different input and output impedance levels. Do not use high impedance probes; they represent a heavy capacitive load to the op amps, and will alter their response. Instead, use low impedance (≤ 500Ω) probes with adequate bandwidth; the probe input capacitance and resistance set an upper limit on the measurement bandwidth. If a high impedance probe must be used, place a 100Ω resistor on the probe tip to isolate its capacitance from the circuit. CIRCUIT SCHEMATIC The circuit schematic in Figure 2 shows the connections for all possible components. Not all of the components are used for each possible configuration. Top View Table I below shows suggested component values for the OPA2650E in three different configurations: Non-Inverting Amplifier (NIA), Inverting Amplifier (IA) and Difference Amplifier (DA). The gain for the Difference Amp is the differential mode gain. Other dual op amps can also be easily set up; see their data sheets to select component values. The resistors R1, R4, R9 and R12 are used to set the input impedance. Resistors R8 and R16 set the output impedance. The values in Table I support test equipment with 50Ω input and output impedances; other source and load impedances are easily accommodated. Output1 1 8 +VS –Input1 2 7 Output2 +Input1 3 6 –Input2 –VS 4 5 +Input2 FIGURE 1. Pin Configuration. C1 and C2 should be size 1206, multi-layer ceramic chip capacitors, or equivalent. C3 and C4 should be size 3528 16V tantalum capacitors. R1 through R16 should be size 1206, metal film chip resistors, or equivalent. J1 - J6 are SMA or SMB connectors. P1 and P2 are power connectors, ED555/2DS from On-Shore Technology. BOARD LAYOUT This evaluation board is a two layer PCB. It uses a ground plane on the bottom, and signal and power traces on the top. The ground plane has been opened up around op amp pins sensitive to capacitive loading. Power supply traces are laid out to keep current loop areas to a minimum. The SMA connectors may be mounted vertically or horizontally. The location and type of capacitors used for power-supply bypassing are crucial to high frequency amplifiers. The tantalum capacitors, C3 and C4, do not need to be as close to pins 8 and 4 on your PCB, and may be shared with other amplifiers. MSOP-8 CONFIGURATION NIA IA Gain +2 –1 DA +1 C1, C2 0.1µF 0.1µF 0.1µF C3, C4 4.7µF 4.7µF 4.7µF R1, R9 49.9Ω Not Used 53.6Ω R2, R10 20.0Ω Not Used 402Ω R3, R11 Not Used 20.0Ω 402Ω R4, R12 Not Used 56.2Ω 61.9Ω R5, R13 Not Used RG = 402Ω RG = 402Ω R6, R14 RG = 402Ω Not Used Not Used R7, R15 RF = 402Ω RF = 402Ω RF = 402Ω R8, R16 49.9Ω 49.9Ω 49.9Ω NOTES: (1) Values shown are for the OPA2650E dual op amp. See the data sheet for information on selecting these values. (2) RF and RG refer to the “feedback” and “gain-setting” resistors for current-feedback op amps. TABLE I. Example Component Selection Guide with 50Ω I/O Impedance. See the data sheet for more information on proper board layout techniques, and component selection. International Airport Industrial Park • Mailing Address: PO Box 11400, Tucson, AZ 85734 • Street Address: 6730 S. Tucson Blvd., Tucson, AZ 85706 • Tel: (520) 746-1111 Twx: 910-952-1111 • Internet: http://www.burr-brown.com/ • Cable: BBRCORP • Telex: 066-6491 • FAX: (520) 889-1510 • Immediate Product Info: (800) 548-6132 © 1997 Burr-Brown Corporation LI-493A Printed in U.S.A. October, 1999 R2 J1 3 +INA R1 2 R3 1/2 OPA26xxE R8 1 J3 OUTA 4 R7 R5 J2 –INA C2 R4 R6 P1 P2 +VS –VS + GND + C3 C4 GND C1 R10 J4 R9 8 5 +INB 6 R11 1/2 OPA26xxE 4 R16 7 J6 OUTB R15 R13 J5 –INB R12 R14 FIGURE 2. Circuit Schematic for DEM-OPA26xxE. FIGURE 4. Bottom Layout with Silk-Screen (bottom view). FIGURE 3. Top Layout with Silk-Screen (top view). The information provided herein is believed to be reliable; however, BURR-BROWN assumes no responsibility for inaccuracies or omissions. BURR-BROWN assumes no responsibility for the use of this information, and all use of such information shall be entirely at the user’s own risk. Prices and specifications are subject to change without notice. No patent rights or licenses to any of the circuits described herein are implied or granted to any third party. BURR-BROWN does not authorize or warrant any BURR-BROWN product for use in life support devices and/or systems. ® DEM-OPA26xxE 2