DEM-OPA68xU ® EVALUATION FIXTURE DESCRIPTION The DEM-OPA68xU demonstration board is an unpopulated printed circuit board (PCB) for BurrBrown’s high speed single op amps available in SO-8 packages. Figure 1 shows the pin out used for most of these op amps. Table I lists the exceptions to this pin-out that are also supported by this board. For more information on these op amps, and good PCB layout techniques, see the individual data sheets. 1 8 NC –In 2 7 +VS +In 3 6 Output –VS 4 5 NC PIN #5 PIN #8 OPA63xU OPA64xU OPA628U OPA680U OPA681U OPA682U OPA686U OPA688U OPA689U — — — — — RG — — — — –VS (optional) –VS — — — — VL VL DIS +VS (optional) +VS DIS DIS DIS DNC(1) VH VH TABLE I. Supported Exceptions to Pinout in Figure 1. CIRCUIT The circuit schematic in Figure 2 shows the connections for all possible components. Each model will only use some of the components. SO-8 NC PIN #2 NOTE: (1) DNC means do not connect. The ordering number for this board is MKT-351. Limit of 5 per customer. Top View PRODUCT COMPONENTS Components that have RF performance similar to the ones in Table II may be substituted. C1 and C2 need a larger voltage rating for ±15V dual supplies. FIGURE 1. Pin Configuration for OPA6xxU. J3 R10 VH/DIS/DIS R9 R3 R2 J1 IN R4 R1 R8 C7 C5 8 3 7 2 R5 5 1 J2 Out 4 C4 C6 R12 R7 6 R6 L2 R11 P1 –VS C3 J4 + C2 GND L1 R13 VL + +VS C1 FIGURE 2. Circuit Schematic for DEM-OPA68xU. 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 © 1998 Burr-Brown Corporation LI-513A Printed in U.S.A. November, 1999 PART DESCRIPTION C1, C2 Tantalum Chip Capacitor, SMD EIA size 3528, 20V C3 - C7 Multi-Layer Ceramic Chip Cap., SMD 1206, 50V J1 - J4 SMA or SMB Board Jack (Amphenol 901-144-8) L1, L2 EMI-Suppression Ferrite Chip, SMD 1206 (Steward LI 1206 B 900 R) P1 Terminal Block, 3.5mm centers (On-Shore Technology ED555/3DS) R1 - R13 Metal Film Chip Resistor, SMD 1206, 1/8W TABLE II. Component Descriptions. R1 and R7 set the I/O impedance, R2 - R6 set the gain, and C1 - C5 are supply bypass capacitors. C3 is optional; it adds a bypass between the supplies, which improves distortion performance for some models. L1 and 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. R8 - R13, C6 and C7 are optional components that support op amps with special functions (see Table I). COMPONENT SINGLE SUPPLY (G = +1) R1 R2 R3 R4 R5 R6 R7 R8 - R13 C1 C2 C3 C4 C5 C6, C7 49.9Ω 10.0Ω Open Open 402Ω 402Ω 49.9Ω Open 2.2µF 2.2µF 0.01µF 0.1µF 0.1µF Open 57.6Ω Open 10.0Ω 402Ω Open 402Ω 49.9Ω Open 2.2µF 2.2µF 0.01µF 0.1µF 0.1µF Open 49.9Ω 10.0Ω Open Open Open 402Ω 49.9Ω Open 2.2µF Open Open 0Ω 0.1µF Open DUAL SUPPLY (G = –1) SINGLE SUPPLY (G = +1) R1 R2 R3 R4 R5 R6 R7 R8 - R13 C1 C2 C3 C4 C5 C6, C7 49.9Ω 178Ω Open Open 402Ω 402Ω 49.9Ω Open 2.2µF 2.2µF 0.01µF 0.1µF 0.1µF Open 57.6Ω Open 210Ω 402Ω Open 402Ω 49.9Ω Open 2.2µF 2.2µF 0.01µF 0.1µF 0.1µF Open 49.9Ω 0Ω Open Open Open 24.9Ω 49.9Ω Open 2.2µF Open Open 0Ω 0.1µF Open TABLE IV. Standard Voltage-Feedback Op Amps. Standard Current-Feedback Op Amps—These op amps have the pinout shown in Figure 1. Table III shows typical values used for these parts. To select component values for your op amp (especially R6), consult its data sheet. DUAL SUPPLY (G = –1) DUAL SUPPLY (G = +2) NOTE: The values and gains shown will not work for all voltage-feedback op amps. See the individual op amp data sheet to select proper values. The I/O impedances are 50Ω. For single supply operation, do not connect L2; otherwise, the –VS input to P1 would be at ground potential. DUAL SUPPLY (G = +2) COMPONENT COMPONENT DUAL SUPPLY (G = )+2 DUAL SUPPLY (G = –1) SINGLE SUPPLY (G = +1) R8, R11 C1 C2 C4, C6 C5, C7 0Ω 4.7µF 4.7µF 0.1µF 0.1µF 0Ω 4.7µF 4.7µF 0.1µF 0.1µF 0Ω 4.7µF Open 0Ω 0.1µF TABLE V. OPA628U and OPA64xU Changes. OPA63xU—Pin 8 disables the output when high (OPA632 and OPA635). Table VII shows different ways to set up pin 8’s voltage using R8, R9 and C7. Use Table IV for the other components, except for the changes shown in Table VI; note these are all single supply configurations. COMPONENT SINGLE SUPPLY SINGLE SUPPLY SINGLE SUPPLY (G = +2) (G = –1) (G = +1) C4 0Ω 0Ω 0Ω TABLE VI. OPA63xU Changes. NOTE: The values and gains shown will not work for all current-feedback op amps. See the data sheet to select proper values. The I/O impedances are 50Ω. TABLE III. Standard Current-Feedback Op Amps. CONFIGURATION R8 C9 External Source On Off Open Open 0Ω 49.9Ω 0Ω Open TABLE VII. Disable Pin—OPA632U and OPA635U. Standard Voltage-Feedback Op Amps—These op amps have the pinout shown in Figure 1. Table IV shows typical values used for these parts. To select component values for your op amp, consult its data sheet. OPA680U—Pin 8 disables the output when low. Table VIII shows different ways to set up pin 8’s voltage using R8, R9 and C7. Use Table IV for the other components. OPA628U and OPA64xU—These op amps have additional supply pins (see Table I) to improve distortion. Use the values in Table IV, except for the changes shown in Table V (the OPA64xP family will function without these changes, but with reduced distortion performance). CONFIGURATION R8 R9 C7 External Source On Off Open Open Open 49.9Ω Open 0Ω Open 0.1µF Open TABLE VIII. Disable Pin—OPA68xU. ® DEM-OPA68xU 2 OPA689U—This VLA™ is the high gain-stable version of the OPA688U. Set up this op amp the same as the OPA688U, except for the changes shown in Table XII. OPA681U—Pin 8 disables the output when low. Table VIII shows different ways to set up pin 8’s voltage using R8, R9 and C7. Use Table III for the other components. OPA682U—The OPA682U uses internal resistors to set the gain at +1, +2, or –1. Pin 8 disables the output when low. Table VIII shows different ways to set up pin 8’s voltage using R8, R9 and C7. Use Table III for the other components, except for the changes shown in Table IX. 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 DUAL SUPPLY (G = –10) SINGLE SUPPLY (G = +20) R1 R2 R3 R4 R5 R6 49.9Ω 20.0Ω Open Open 49.9Ω 453Ω Open Open 10.0Ω 49.9Ω Open 499Ω 49.9Ω 10.0Ω Open Open 26.1Ω 499Ω DUAL SUPPLY (G = –6) SINGLE SUPPLY (G = +6) R1 R2 R3 R4 R5 R6 49.9Ω 100Ω Open Open 150Ω 750Ω 82.5Ω Open 130Ω 124Ω Open 750Ω 49.9Ω 100Ω Open Open 150Ω 750Ω 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. OPA686U—Use Table X for the higher gains needed by this part, and Table IV for the other component values. Extra care is needed to ensure pin 8 is not connected (see Table I). DUAL SUPPLY (G = +10) DUAL SUPPLY (G = +6) TABLE XII. OPA689U Changes. TABLE IX. OPA682U Changes. COMPONENT COMPONENT 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 pins 7 and 4 on your PCB, and may be shared with other amplifiers. See the individual op amp data sheet for more information on proper board layout techniques, and component selection. TABLE X. OPA686U Changes. OPA688U—This VLA™ (Voltage Limiting Amplifier) has two inputs (VH and VL in Table I), which limit the output voltage swing. Table XI shows different ways to set up pin 5’s and pin 8’s voltages using R8 - R13 and C5 - C7. Use Table IV for the other components. 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. Change the component values for different input and output impedance levels. Note that this board would require modification for the single-supply circuit shown in the OPA688 data sheet. In dual supply applications, using R10 instead of R8 makes VH negative, and using R13 instead of R11 makes VL positive. COMPONENT DUAL SUPPLY (G = +2) DUAL SUPPLY (G = –1) SINGLE SUPPLY (G = +1) R8 R9 R11 R12 R13 C5 - C7 3.01kΩ 1.91kΩ 3.01kΩ 1.91kΩ Open 0.1µF 3.01kΩ 1.91kΩ 3.01kΩ 1.91kΩ Open 0.1µF 549Ω 1.58kΩ Open 549Ω 1.58kΩ 0.1µF 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 XI. Limiting Pins—OPA68xU. ® 3 DEM-OPA68xU (a) (b) FIGURE 3. DEM-OPA68xU Demonstration Board Layout; (a) Component Side Silkscreen and Metal, (b) Ground Plane Side Silkscreen and Metal (bottom view). ® DEM-OPA68xU 4