DEM-OPA368xU ® EVALUATION FIXTURE DESCRIPTION COMPONENTS Components that have RF performance similar to the ones in Table I may be substituted. The DEM-OPA368xU demonstration board is an unpopulated printed circuit board (PCB) for the high speed triple op amps with disable available in SO-16 packages. The DEM-OPA368xU supports BurrBrown’s OPA3680U, OPA3681U, and OPA3682U. Figure 1 shows the package pinout for this PCB. For more information on these op amps, and good PCB layout techniques, see the individual op amp data sheets. R1 and R7 set the I/O impedance, R2 - R6 set the gain, R8 and C8 set up the disable pin, and C1 - C7 are supply bypass capacitors. C3 is optional; it adds a bypass between the supplied, which improves distortion performance for some models. L1 - L2 are ferrite chips that can reduce interactions with the power supply at high frequencies; if not desired, they can be replaced with 0Ω resistors. The ordering number for this board is MKT-364. Limit of 5 per customer. For single supply operation, do not connect L2; otherwise, the –VS input to P1 would be at ground potential. CIRCUIT The circuit schematic in Figure 2 shows the connections for all possible components. Each model will only use some of the components. Top View J3A SO-16 DIS A –IN A 1 +IN A 2 16 DIS A 15 +VS J1A IN A DIS B 3 14 OUT A –IN B 4 13 –VS +IN B 5 12 OUT B DIS C 6 11 +VS R1A P1 R2A 2 R4A 1 7 16 14 C6 8 C4 L2 + GND C2 C3 L1 + C5 C1 J3B DIS B –VS J1B IN B R1B DESCRIPTION C1, C2 Tantalum Chip Capacitor, SMD EIA size 3528, 20V C3 - C8C Multi-Layer Ceramic Chip Cap., SMD 1206, 50V J1A - J3C SMA or SMB Board Jack (Amphenol 901-144-8) L1, L2 P1 R1A - R8C C8B R3B FIGURE 1. Pin Configuration. PART Out A –VS 10 OUT C 9 J2A R6A C7 +IN C R7A 9, 13 R5A +VS –IN C R8A C8A R3A R2B 5 R4B 4 11, 15 3 12 R8B R7B J2B Out B R6B R5B J3C DIS C C8C R3C J1C EMI-Suppression Ferrite Chip, SMD 1206 (Steward LI 1206 B 900 R) IN C R1C Terminal Block, 3.5mm centers (On-Shore Technology ED555/3DS) R2C 8 R4C 7 R5C 6 10 R8C R7C J2C Out C R6C Metal Film Chip Resistor, SMD 1206, 1/8W FIGURE 2. Circuit Schematic for DEM-OP368xU. TABLE I. Part Descriptions. 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 © 1999 Burr-Brown Corporation LI-546 Printed in U.S.A. December, 1999 BOARD LAYOUT This demonstration 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 (or SMB) connectors may be mounted either vertically or horizontally. Disable Pins—Pins 16, 3 and 6 disable op amps A, B and C when low. Table II shows different ways to set up these pins’ voltages. CONFIGURATION R8 C6 External Source On Off 49.9Ω Open 0Ω Open 0.1µF Open The location and type of capacitors used for power-supply bypassing are crucial to high frequency amplifiers. The tantalum capacitors, C1 and C2, do not need to be as close to the supply pins on your PCB and may be shared with other amplifiers. TABLE II. Disable Pin—OPA368xU. OPA3680U—Table III shows typical values for this part. For more information, consult the data sheet. COMPONENT DUAL SUPPLY (G = +2) DUAL SUPPLY (G = –1) SINGLE SUPPLY (G = +1) R1 R2 R3 R4 R5 R6 R7 C1, C2 C3 C4 - C7 49.9Ω 178Ω Open Open 402Ω 402Ω 49.9Ω 2.2µF 0.01µF 0.1µF 57.6Ω Open 210Ω 402Ω Open 402Ω 49.9Ω 2.2µF 0.01µF 0.1µF 49.9Ω 0Ω Open Open Open 24.9Ω 49.9Ω 2.2µF Open 0.1µF See the individual op amp data sheet for more information on proper board layout techniques, and component selection. MEASUREMENT TIPS This demonstration 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. NOTE: The I/O impedances are 50Ω. 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. TABLE III. OPA3680U. OPA3681U—Table IV shows typical values for this part. For more information, consult the data sheet. COMPONENT DUAL SUPPLY (G = +2) DUAL SUPPLY (G = –1) SINGLE SUPPLY (G = +1) R1 R2 R3 R4 R5 R6 R7 C1, C2 C3 C4 - C7 49.9Ω 10.0Ω Open Open 402Ω 402Ω 49.9Ω 2.2µF 0.01µF 0.1µF 57.6Ω Open 10.0Ω 402Ω Open 402Ω 49.9Ω 2.2µF 0.01µF 0.1µF 49.9Ω 10.0Ω Open Open Open 402Ω 49.9Ω 2.2µF Open 0.1µF NOTE: The I/O impedances are 50Ω. TABLE IV. OPA3681U. OPA3682U—The OPA3682U uses internal resistors to set the gain at +1, +2, or –1. Use Table IV for the components, except for the changes in Table V. COMPONENT DUAL SUPPLY (G = +2) DUAL SUPPLY (G = –1) SINGLE SUPPLY (G = +1) R4 R5 R6 Open 0Ω Open 0Ω Open Open Open Open Open NOTE: The I/O impedances are 50Ω. TABLE V. OPA3682U Changes. ® DEM-OPA368xU 2 (a) (b) FIGURE 3. DEM-OPA368xU Demonstration Board Layout; (a) Component Side Silkscreen and Metal, (b) Ground Plane Side Silkscreen and Metal (bottom view). ® 3 DEM-OPA368xU