Motore di ricerca datesheet componenti elettronici |
|
DAC0832LCJ Scheda tecnica(PDF) 13 Page - National Semiconductor (TI) |
|
|
DAC0832LCJ Scheda tecnica(HTML) 13 Page - National Semiconductor (TI) |
13 / 28 page DAC0830 Series Application Hints (Continued) Always use the internal R fb resistor to create an output voltage since this resistor matches (and tracks with tempera- ture) the value of the resistors used to generate the output current (I OUT1). 2.3 Op Amp Considerations The op amp used in Figure 7 should have offset voltage nulling capability (See Section 2.5). The selected op amp should have as low a value of input bias current as possible. The product of the bias current times the feedback resistance creates an output voltage error which can be significant in low reference voltage appli- cations. BI-FET™ op amps are highly recommended for use with these DACs because of their very low input current. Transient response and settling time of the op amp are important in fast data throughput applications. The largest stability problem is the feedback pole created by the feed- back resistance, R fb, and the output capacitance of the DAC. This appears from the op amp output to the (−) input and includes the stray capacitance at this node. Addition of a lead capacitance, C C in Figure 8, greatly reduces overshoot and ringing at the output for a step change in DAC output current. Finally, the output voltage swing of the amplifier must be greater than V REF to allow reaching the full scale output voltage. Depending on the loading on the output of the amplifier and the available op amp supply voltages (only ±12 volts in many development systems), a reference voltage less than 10 volts may be necessary to obtain the full analog output voltage range. 2.4 Bipolar Output Voltage with a Fixed Reference The addition of a second op amp to the previous circuitry can be used to generate a bipolar output voltage from a fixed reference voltage. This, in effect, gives sign significance to the MSB of the digital input word and allows two-quadrant multiplication of the reference voltage. The polarity of the reference can also be reversed to realize full 4-quadrant multiplication: ±V REFx±Digital Code= ±VOUT. This circuit is shown in Figure 9. This configuration features several improvements over exist- ing circuits for bipolar outputs with other multiplying DACs. Only the offset voltage of amplifier 1 has to be nulled to preserve linearity of the DAC. The offset voltage error of the second op amp (although a constant output voltage error) has no effect on linearity. It should be nulled only if absolute output accuracy is required. Finally, the values of the resis- tors around the second amplifier do not have to match the internal DAC resistors, they need only to match and tem- perature track each other. A thin film 4-resistor network available from Beckman Instruments, Inc. (part no. 694-3-R10K-D) is ideally suited for this application. These resistors are matched to 0.1% and exhibit only 5 ppm/˚C resistance tracking temperature coefficient. Two of the four available 10 k Ω resistors can be paralleled to form R in Figure 9 and the other two can be used independently as the resistances labeled 2R. 00560837 FIGURE 6. 00560838 FIGURE 7. www.national.com 13 |
Codice articolo simile - DAC0832LCJ |
|
Descrizione simile - DAC0832LCJ |
|
|
Link URL |
Privacy Policy |
ALLDATASHEETIT.COM |
Lei ha avuto il aiuto da alldatasheet? [ DONATE ] |
Di alldatasheet | Richest di pubblicita | contatti | Privacy Policy | scambio Link | Ricerca produttore 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 |