 |
поискавой системы для электроныых деталей |
|
|
поискавой системы для электроныых деталей |
|
ADA4945-1ACPZ-R2 датащи(PDF) 39 Page - Analog Devices |
|
|
|||||||||||||||||||||||||||||
ADA4945-1ACPZ-R2 датащи(HTML) 39 Page - Analog Devices |
|
|
39 / 44 page  Data Sheet ADA4945-1 Rev. 0 | Page 39 of 44 Terminating a Single-Ended Input This section describes how to properly terminate a single-ended input to the ADA4945-1. Assume a system gain of 1 where RF1 = RF2 = RG1 = RG2 = 499 Ω, an input source with an open-circuit output voltage of 2 V p-p, and a source resistance of 50 Ω. Figure 105 shows the circuit. 1. Calculate the input impedance. β1 = β2 = 499/998 = 0.5 and RIN = 665.33 Ω RS 50Ω VS 2V p-p RIN 665.333Ω ADA4945-1 RL VOUT, dm +VS –VS RG1 499Ω RG2 499Ω RF2 499Ω RF1 499Ω VOCM Figure 105. Single-Ended Input Impedance RIN 2. Add a termination resistor (RT) to match the 50 Ω source resistance. Because RT||665.33 Ω = 50 Ω, RT = 54.06 Ω. ADA4945-1 RL VOUT, dm +VS –VS RS 50Ω RG1 499Ω RG2 499Ω RF2 499Ω RF1 499Ω VOCM VS 2V p-p RIN 50Ω RT 54.06Ω Figure 106. Adding Termination Resistor, RT 3. Replace the source termination resistor combination with the Thevenin equivalent. The Thevenin equivalent of the source resistance, RS, and the termination resistance, RT, is RTH = RS||RT = 25.976 Ω. The Thevenin equivalent of the source voltage is VTH = VS T S T R R R + = 1.039 V p-p RS 50Ω VS 2V p-p RT 54.06Ω RTH 25.976Ω VTH 1.039V p-p Figure 107. Thevenin Equivalent Circuit 4. Set RF1 = RF2 = RF to maintain a balanced system. Compensate the imbalance caused by RTH. There are two methods available to compensate, as follows: • Add RTH to RG2 to maintain balanced gain resistances and increase RF1 and RF2 to RF = TH S V V Gain(RG + RTH) to maintain the system gain. • Decrease RG2 to RG2 = Gain V V R S TH F × × to maintain system gain and decrease RG1 to (RG2 − RTH) to maintain balanced gain resistances. The first compensation method is used in the Analog Devices DiffAmpCalc™ tool. Using the second compensation method, RG2 =259.241 Ω and RG1 = 259.241 – 25.976 = 233.265 Ω. The modified circuit is shown in Figure 108. ADA4945-1 RL VOUT, dm +VS –VS RTH 25.976Ω RG1 233.265Ω RG2 259.241Ω RF2 499Ω RF1 499Ω VOCM VTH 1.039V p-p Figure 108. Thevenin Equivalent with Matched Gain Resistors Figure 108 shows an easily manageable circuit with matched feedback loops that can be easily evaluated. 5. The modified gain resistor, RG1, changes the input impedance. Repeat Step 1 through Step 4 several times using the modified value of RG1 from the previous iteration until the value of RT does not change from the previous iteration. After three additional iterations, the change in RG1 is less than 0.1%. The final circuit is shown in Figure 109 with the closest 1% resistor values. ADA4945-1 RL VOUT, dm 1.990V p-p +VS –VS RS 50Ω RG 243Ω VP VN RG2 267Ω RF1 499Ω RF2 499Ω VOCM VS 2V p-p 0.998V p-p RT 57.6Ω Figure 109. Terminated Single-Ended-to-Differential System with G = 1 |
|
ссылки URL |
| Вашему бизинису помогли Аллдатащит? [ DONATE ] |
Что такое Аллдатащит | реклама | контакт | Конфиденциальность | Ссылка на техническое описание | обмен ссыками | поиск по производителю 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 |
Russian ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
