 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
LMC6464AIMX Datasheet(PDF) 10 Page - National Semiconductor (TI) |
|
|
||||||||||||||||||||||||||||||
LMC6464AIMX Datasheet(HTML) 10 Page - National Semiconductor (TI) |
|
|
10 / 18 page  Application Information (Continued) 2.0 Rail-to-Rail Output The approximated output resistance of the LMC6462/4 is 180 Ω sourcing, and 130Ω sinking at V S = 3V, and 110Ω sourcing and 83 Ω sinking at V S = 5V. The maximum output swing can be estimated as a function of load using the calcu- lated output resistance. 3.0 Capacitive Load Tolerance The LMC6462/4 can typically drive a 200 pF load with V S = 5V at unity gain without oscillating. The unity gain follower is the most sensitive configuration to capacitive load. Direct ca- pacitive loading reduces the phase margin of op-amps. The combination of the op-amp’s output impedance and the ca- pacitive load induces phase lag. This results in either an un- derdamped pulse response or oscillation. Capacitive load compensation can be accomplished using resistive isolation as shown in Figure 4. If there is a resistive component of the load in parallel to the capacitive compo- nent, the isolation resistor and the resistive load create a voltage divider at the output. This introduces a DC error at the output. Figure 5 displays the pulse response of the LMC6462/4 cir- cuit in Figure 4. Another circuit, shown in Figure 6, is also used to indirectly drive capacitive loads. This circuit is an improvement to the circuit shown in Figure 4 because it provides DC accuracy as well as AC stability. R1 and C1 serve to counteract the loss of phase margin by feeding the high frequency component of the output signal back to the amplifiers inverting input, thereby preserving phase margin in the overall feedback loop. The values of R1 and C1 should be experimentally de- termined by the system designer for the desired pulse re- sponse. Increased capacitive drive is possible by increasing the value of the capacitor in the feedback loop. The pulse response of the circuit shown in Figure 6 is shown in Figure 7. 4.0 Compensating for Input Capacitance It is quite common to use large values of feedback resis- tance with amplifiers that have ultra-low input current, like the LMC6462/4. Large feedback resistors can react with small values of input capacitance due to transducers, photo- diodes, and circuits board parasitics to reduce phase margins. DS012051-7 FIGURE 3. Input Current Protection for Voltages Exceeding the Supply Voltage DS012051-8 FIGURE 4. Resistive Isolation of a 300 pF Capacitive Load DS012051-9 FIGURE 5. Pulse Response of the LMC6462 Circuit Shown in Figure 4 DS012051-10 FIGURE 6. LMC6462 Non-Inverting Amplifier, Compensated to Handle a 300 pF Capacitive and 100 k Ω Resistive Load DS012051-11 FIGURE 7. Pulse Response of LMC6462 Circuit in Figure 6 www.national.com 10 |
Similar Part No. - LMC6464AIMX |
|
Similar Description - LMC6464AIMX |
|
|
|
Link URL |
| Privacy Policy |
| ALLDATASHEET.NET |
| Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | 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
