 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
OPA228PA Datasheet(PDF) 11 Page - Burr-Brown (TI) |
|
|
||||||||||||||||||||||||||||||
OPA228PA Datasheet(HTML) 11 Page - Burr-Brown (TI) |
|
|
11 / 25 page  OPA227, 2227, 4227 OPA228, 2228, 4228 11 SBOS110A www.ti.com FIGURE 1. OPA227 Offset Voltage Trim Circuit. APPLICATIONS INFORMATION The OPA227 and OPA228 series are precision op amps with very low noise. The OPA227 series is unity-gain stable with a slew rate of 2.3V/ µs and 8MHz bandwidth. The OPA228 series is optimized for higher-speed applications with gains of 5 or greater, featuring a slew rate of 10V/ µs and 33MHz bandwidth. Applications with noisy or high impedance power supplies may require decoupling capacitors close to the device pins. In most cases, 0.1 µF capacitors are ad- equate. OFFSET VOLTAGE AND DRIFT The OPA227 and OPA228 series have very low offset voltage and drift. To achieve highest dc precision, circuit layout and mechanical conditions should be optimized. Connections of dissimilar metals can generate thermal po- tentials at the op amp inputs which can degrade the offset voltage and drift. These thermocouple effects can exceed the inherent drift of the amplifier and ultimately degrade its performance. The thermal potentials can be made to cancel by assuring that they are equal at both input terminals. In addition: • Keep thermal mass of the connections made to the two input terminals similar. • Locate heat sources as far as possible from the critical input circuitry. • Shield op amp and input circuitry from air currents such as those created by cooling fans. OPERATING VOLTAGE OPA227 and OPA228 series op amps operate from ±2.5V to ±18V supplies with excellent performance. Unlike most op amps which are specified at only one supply voltage, the OPA227 series is specified for real-world applications; a single set of specifications applies over the ±5V to ±15V supply range. Specifications are assured for applications between ±5V and ±15V power supplies. Some applications do not require equal positive and negative output voltage swing. Power supply voltages do not need to be equal. The OPA227 and OPA228 series can operate with as little as 5V between the supplies and with up to 36V between the supplies. For example, the positive supply could be set to 25V with the negative supply at –5V or vice-versa. In addition, key parameters are assured over the specified temperature range, –40 °C to +85°C. Parameters which vary significantly with operating voltage or temperature are shown in the Typical Performance Curves. OFFSET VOLTAGE ADJUSTMENT The OPA227 and OPA228 series are laser-trimmed for very low offset and drift so most applications will not require external adjustment. However, the OPA227 and OPA228 (single versions) provide offset voltage trim con- nections on pins 1 and 8. Offset voltage can be adjusted by connecting a potentiometer as shown in Figure 1. This adjustment should be used only to null the offset of the op amp. This adjustment should not be used to compensate for offsets created elsewhere in the system since this can introduce additional temperature drift. INPUT PROTECTION Back-to-back diodes (see Figure 2) are used for input protec- tion on the OPA227 and OPA228. Exceeding the turn-on threshold of these diodes, as in a pulse condition, can cause current to flow through the input protection diodes due to the amplifier’s finite slew rate. Without external current-limiting resistors, the input devices can be destroyed. Sources of high input current can cause subtle damage to the amplifier. Although the unit may still be functional, important param- eters such as input offset voltage, drift, and noise may shift. FIGURE 2. Pulsed Operation. When using the OPA227 as a unity-gain buffer (follower), the input current should be limited to 20mA. This can be accom- plished by inserting a feedback resistor or a resistor in series with the source. Sufficient resistor size can be calculated: RX = VS/20mA – RSOURCE where RX is either in series with the source or inserted in the feedback path. For example, for a 10V pulse (VS = 10V), total loop resistance must be 500 Ω. If the source impedance is large enough to sufficiently limit the current on its own, no additional resistors are needed. The size of any external resistors must be carefully chosen since they will increase noise. See the Noise Performance section of this data sheet for further information on noise calcula- tion. Figure 2 shows an example implementing a current- limiting feedback resistor. OPA227 20k Ω 0.1 µF 0.1 µF 2 1 7 8 6 3 4 V+ V– Trim range exceeds offset voltage specification OPA227 and OPA228 single op amps only. Use offset adjust pins only to null offset voltage of op amp. See text. OPA227 Output R F 500 Ω Input – + |
Similar Part No. - OPA228PA |
|
Similar Description - OPA228PA |
|
|
|
Link URL |
| Privacy Policy |
| ALLDATASHEET.COM |
| Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Datasheet Upload | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
| Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
|
Family Site : ic2ic.com |
icmetro.com |
English ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
