Q: I have seen power op amps available in small metal hybrid packages or monolithic amplifiers in small plastic packages. How are your products different?
A: Hybrid amplifiers are generally expensive and are often meant for military applications. You must mount the hybrid to a heat sink to be of any practical use in most cases. Once the hybrid is mounted to a heat sink the total amplifier is not small. The total volume utilized includes not only the amplifier but also the footprint of the heat sink as well. Our amplifiers can dissipate more power as built on their heat sinks than most hybrids can when mounted on an infinite heat sink. Monolithic amplifiers, while small, also cannot handle the power dissipation of our amplifiers. In the end it?s the power dissipation capability of the amplifier that determines the usefulness of an amplifier in a power application. Our new line of compact power amps approach the footprint of the small hybrid amplifiers with a footprint only 40mm square. This makes our compact amplifiers only slightly longer and wider than a hybrid TO3 package, and our amplifiers include the heat sink in the same footprint.
Q: Why do your amplifier products only come with 12V fans?
A: Our fans can run on voltages of 7-17V although the amplifier?s rating applies to 12-15V operation. These seem to be the most common voltages available, but, upon request, we can also supply fans with voltage ratings of 5V or 24V with equal performance.
Q:I am concerned with the reliability of the fan cooling your amplifiers use. What is the mean time to failure (MTBF) of your fans.
A: We use the best fan products available with double ball and double sealed bearings and a fan temperature rating of 70OC. MTBF refers to the hours of operation needed for 50% of a fan population to fail. Our fans are rated for a MTBF of 250k hours. However, we use the more conservative L10 rating. The L10 rating refers to the time it takes for 10% of a population of fans to fail. Our fans are rated for an L10 of 60k hours at 50OC and 90k hours at 25OC. In addition, we offer the PAD131 Fan Controller Accessory Module that keeps the fan rpm at the minimum necessary for proper amplifier temperature control. In many amplifier applications maximum power dissipation is not always required. The PAD131 lowers the rpm when maximum amplifier power dissipation is not needed. Since the leading cause of fan failure is bearing wear, we believe that lowering the rpm will increase fan life (lower rpm also reduces audible noise).
Q: I have a special situation in my application and I need to use a custom passive heat sink. Can I buy your amplifiers without the heat sink and fan?
A: Our amplifiers are often used in special applications where our heat sink and fan is not needed or not consistent with mechanical requirements of the customer. Upon request we can quote the amplifier without the heat sink and fan. We also have supplied our amplifiers mounted on custom passive heat sinks for our customers.
Q: Why do I need an accessory module to make your amplifier work?
A: Accessory modules are always optional and you don?t need an accessory module to make your amplifier work. However, accessory modules can offer other modes of operation or extended capability for the amplifier in some applications. The amplifier evaluation kits often provide sockets where accessory modules can be plugged in and evaluated with the amplifier.
Q: Are your amplifiers suitable for operation as audio amplifiers?
A: There is no engineering reason why our amplifiers cannot be used as audio amplifiers but we don't stress that application. Customers looking for audio amplifiers have many choices available and don't usually consider a power op amp for that application. In addition, power op amps must perform well in many ways that an audio amplifier does not. For example, power op amps need to amplify DC signals as well as AC signals accurately and audio amplifiers do not need DC accuracy and, in fact, usually eliminate any DC at the output. Power op amps are also distinquished from audio amplifiers by the need to operate over a wide range of power supply voltages, both balanced and not. In addition, power op amps need to operate well over industrial temperature ranges and audio amplifiers usually do not. Some of our power op amps do have low distortion ratings and make fine audio power amplifiers, but they are rarely used for that application (PAD128 and PAD129 for example).
Q: Why don?t your amplifiers come with some sort of cover over the circuitry?
A: Any sort of cover increases cost and does not provide any additional protection for the amplifier. Most of the circuitry is already covered by a printed soldermask layer. The exposed components of the amplifier circuitry are quite reliable as they are without any additional protection. Finally, when the amplifier is mounted to the motherboard the circuitry is covered by the motherboard. In short, any sort of cover increases cost without any real reliability benefit. In some applications a conformal coat is beneficial and we can provide that service at additional cost.
Q: Some manufacturers give away their product evaluation kits. Why don?t you?
A: Our evaluation kits are extensive and provide components that are not usually found in engineering labs. Power amp applications often require somewhat specialized components and we provide these rather than expect our customers to research and procure such components. Even though we charge a fee for our kits we think they represent good value since the kits save time and ensure that the proper components are available to develop the application circuit in a timely way.
Q: Why don't your evaluation kits include the amplifier? A: There are several reasons. We try to keep amplifier models in stock for quick delivery of a few pieces and we don't like to tie up our stock of amplifiers in evaluation kits. Also, evaluation kits support optional accessory modules. If we included the amplifier why not also the accessory modules? This approach would raise the overall cost of the evaluation kit. And finally, we have customers that purchase the evaluation kit and not the amplifier. Their approach is to develop several circuits with one amplifier to reduce their overall development costs. Sometimes our customers also use the evaluation kit board as an incoming test platform for the amplifiers they regularly purchase. We felt the best overall approach is to price the evaluation kit as a stand-alone item and let the customer purchase any or all of the amplifiers and accessory modules as they see fit for their application.