1. Passives What Are Passives? What Do They Do?
What’s Out There To Choose From?
Which One Is Right For Me?
Starting Slide

2. What Are Passives?
Passives are components that can function without a separate power supply
The most common are:
- Resistors
- Capacitors
- Inductors
There are also diodes, but they won’t be discussed here.

3. What Do They Do? Basics Common Uses in APA Applications Resistors
Capacitors
Inductors
Common Uses in APA Applications

4. What Do They Do? Basics Resistors Capacitors Inductors
Resists Electrical Potential
Resistivity is constant across the frequency
band
No energy is stored, only dissipated
Capacitors
Stores energy in the electric field
Inductors
Store energy in the magnetic field
Inductors are discussed on next page

5. What Do They Do? Common Uses in APA Applications Resistors
Voltage Dividers
Gain Setting
Current Limiting
Filtering
RC filter may be used to filter the output of a class-D
Voltage dividers can be used to set the bias voltage
Gain setting is used in such parts as the TPA6120A2, TPA6211A1, TPA0211

6. What Do They Do? Common Uses in APA Applications Capacitors
DC Blocking
Power Supply
Decoupling
Filtering
RC Filter may be used to filter the output of a class-D
Always use power supply decoupling
DC blocking caps are used in almost all of our amplifiers.

7. What Do They Do? Common Uses in APA Applications Inductors
Output Filtering
EMI Blocking
Power Supply
Filtering
LC Filter may be used to filter the output of a class-D
Sometimes Inductors are used to Filter the Power Supply. Be careful that the inductor has the proper current rating so that it won’t be destroyed, current limit the device, or saturate.
Won’t be discussing EMI here

8. What’s Out There to Choose From?
Mounting Methods
Resistors
Capacitors
Inductors

9. What’s Out There to Choose From?
Mounting Methods
Thru-Hole
Applies to Resistors, Capacitors, and Inductors
Component has metal leads that go through holes on the board
Surface Mount
Component has no leads. It is soldered directly down to pads on the board
Surface Mount is the best way to go. Leaded parts can act like antennas.

10. What’s Out There to Choose From?
Resistors
Thin Film
Low Distortion
Excellent TCR (typical between +/-5 and +/-50 PPM/oC)
Excellent Tolerance (typical between 0.01 to 0.5%)
Low Power Ratings are Common (<1W, often much less)
Subject to long lead times
Thin Film is best for Hi-Fi
AP is not equipped to detect the noise/distortion difference between thin film and thick film or even carbon.

11. What’s Out There to Choose From?
Resistors
Thick Film
Higher Distortion than Thin Film
Good TCR (typical between +/-100 and +/-300, but can go up to +/-1000 PPM/oC)
Good Tolerance (typical between 1 and 5%)
Low Power Ratings are Common (<1W, often much less)
Thick Film is basically a shielded ceramic.

12. What’s Out There to Choose From?
Resistors
Ceramic
High Distortion
TCR is poor (typical > 1000 PPM/oC)
Tolerance (typical between 5 to 10%)
Generally thru-hole only

13. What’s Out There to Choose From?
Resistors
Carbon Film
Highest Distortion
TCR can vary greatly (typical between +/-300 and greater than PPM/oC)
Tolerance (typical >5%)
Generally thru-hole only

14. What’s Out There to Choose From?
Capacitors
Film (PPS – Polyphenylene Sulfide,
Polypropylene, Polystyrene, Polyester)
Can have low ESR
Values up to 1uF (typically much lower)
TCR < 1% DC/oC
Tolerance from +/-2% to +/-10%
No Piezoelectric Effect
No Shock Noise
No audible noise
High Stability
0.1395uF/mm3 (ECPU1E105J/K105, 25Vdc)
See app note on page
PPS is the best because it has best performance temp and frequency, as well as distortion and dielectric effect. Only goes up to .22uF
ECPU(A) is second best for values above .22uF (in panasonic line).
See Panasonic’s line of specialty polymers for large value (up to 400+uF) caps that have low esr, low distortion, very good temp coefficients

15. What’s Out There to Choose From?
Capacitors
MLCC (Multilayer Ceramic Chip)
Can have low ESR Values up to and
greater than 100uF
Different types have different ratings
B TCR= +/10%, Tol = +/-10%, +/-20%
X7R TCR= +/-15%, Tol = +/-10%, +/-20%
X5R TCR= +/-15%, Tol = +/-10%, +/-20%
F TCR= +30, -80% Tol = +80, -20%
Y5V TCR= +22, -82%, Tol = +80, -20%
Noisier than Film
10 to 20dB more distortion than Film
0.32uF/mm3 (ECJ2FF1E105Z)
Film is best, but ceramics have a wider range of values to play with.

16. What’s Out There to Choose From?
Capacitors
Tantalum
Can have low ESR
High capacitance values available
Can operate over a broad voltage range
TCR typically +/-10% DC/oC
Tolerance from +/-5% to +/-20%
Price and availability fluctuate.
0.1221uF/mm3 (Kemet T491A105M025AS)
0.0014uF/mm3 (AVX TAJD107K020R)
Kemet is 1uF, 25V device
AVX is 100uF, 20V device.

17. What’s Out There to Choose From?
Capacitors
Electrolytic
Can have low ESR
Extremely High capacitance values
available
Can operate over a broad voltage range
Tolerance typically +/-20%
Very noisy
High Distortion
Large Footprint
0.0032uF/mm3 (EEUFM1E101)
Should be used for bulk decoupling. Avoid putting in the signal path if at all possible.

18. What’s Out There to Choose From?
Capacitors
ESR
ESR is Equivalent Series Resistance
Will cause a voltage drop, even when the cap looks like a “short”
ESL
ESL is Equivalent Series Inductance
After a certain frequency, the capacitor begins to “look” like an inductor. The impedance goes up as the frequency goes up.
Should be used for bulk decoupling. Avoid putting in the signal path if at all possible.

19. What’s Out There to Choose From?
Capacitors
Should be used for bulk decoupling. Avoid putting in the signal path if at all possible.

20. What’s Out There to Choose From?
Inductors
Wound Coil
A length of wire wrapped around a core. Can be an air core. Must be shielded.
Torroid Core
A donut shaped piece of magnetic material around which a wire is wrapped. High Q, small size, compact, good at high frequencies, self shielding.
Ferrite Bead
Inductive material that maintains a low impedance throughout the low frequency range, but a high impedance at high frequencies.
Common Mode Choke
Typically made of a Torroid Core, Common Mode Chokes are used to reduce noise across long lengths of line.
List goes on…

21. Which One Is Right For Me?
What’s the Application?
Other Factors
Guidelines

22. Which One Is Right For Me?
What’s the Application?
Is component noise an issue?
No – System could be noisy to begin with
Yes – Quiet system, such as Hi-Fi
Is the component in the signal path?
No – A pullup resistor, a power supply
decoupling cap, inductor in the power
supply path.
Yes – Gain setting resistors, dc blocking caps, inductors used for filtering the output.
Is this a proof of concept prototype or a final
product?

23. Which One Is Right For Me?
Other Factors
Cost
Lead time
Is what I want even manufactured?

24. Which One Is Right For Me?
Guidelines
Resistors
Signal path of quiet system
Thin Film
Signal path of noisy system
Thick Film
Out of signal path
Thick Film, Ceramic, Carbon Film
Lead Times Unacceptable
Proof of Concept
All will work

25. Which One Is Right For Me?
Guidelines
Capacitors
Signal path of quiet system
PPS, Polypropylene, other film
Low ESR!
Signal path of noisy system
MLCC, Tantalum
Power supply decoupling
MLCC, Electrolytic, Tantalum
Output Filtering
Film, MLCC
Electrolytic may be better than Tantalum for power supply decoupling because of the large bulk sizes and the relative market stability. Electrolytics tend to have low ESR
Look at Panasonic’s SPCaps for output coupling.

26. Which One Is Right For Me?
Guidelines
Inductors
Proper choice for use (ferrite bead, common mode choke, etc.)
Correct Value!
Correct Current Rating
Correct Frequency Rating
Low DCR!
Proper choice for use has mostly to do with EMI. This will deal with filters.

27. Which One Is Right For Me?
Guidelines
Inductors
Correct Value
Correct Value is Critical
Failure to get correct value can cause:
Shift in cutoff frequency
Peaking
High current draw
Inductor saturation
Always err on the side of caution! Best to make
the inductor too big rather than too small!
Proper choice for use has mostly to do with EMI. This will deal with filters.

28. Which One Is Right For Me?
F = cutoff frequency
Lp = Ln. C1=C2=10% of 2Cf

29. Which One Is Right For Me?
Inductor Choices
RL = 8W
Peak will cause problems. Inductor value was too low. The capacitance had to be changed to get the same cutoff frequency. Would have been better to have a higher inductance value and a lower capacitance value.

30. Which One Is Right For Me?
Guidelines
Inductors
Correct Current Rating
Check ISAT of inductor. Ensure it is greater
than maximum current draw
Look at curves in inductor datasheet.
Inductance vs. Current curves will indicate how
the inductance drops with current. May be of more value than just ISAT.
Correct Frequency Rating
Check manufacturer curves to determine at what
frequencies the inductance starts to roll off.
Low DCR!
The lower the better!
Proper choice for use has mostly to do with EMI. This will deal with filters.

31. Which One Is Right For Me?
Inductance vs. Current