# How a Radio Amplifier Saves Energy by Sharing Work > This patent describes a power amplifier design that dynamically adjusts the power supplied to two amplifier stages based on the strength of the incoming radio signal, making it more efficient. - **Patent:** US 5757229 - **Original title:** Bias circuit for a power amplifier - **Owner:** Motorola - **Granted:** 1998 - **Status:** Public domain (expired) - **Times cited:** 94 - **Field:** telecommunications, consumer_electronics, semiconductors, software ## What it does This patent describes a power amplifier that improves efficiency by dynamically adjusting how two internal amplifiers operate. It starts by splitting an incoming radio frequency (RF) signal into two parts: an "in-phase" signal and a "quadrature phase" signal using a power divider (Claim 1). A "carrier amplifier" boosts the in-phase signal, and a "peaking amplifier" boosts the quadrature phase signal (Claim 1). The clever part is how the power supplied to these amplifiers (their "bias inputs") is controlled. As the strength of the incoming RF signal changes, the bias to the carrier amplifier decreases while the bias to the peaking amplifier increases (Claim 1). This ensures that the amplifiers only work as hard as needed, saving energy. Finally, the boosted signals are combined to create the strong output signal (Claim 1). For example, when a cell phone transmits a weak signal, the carrier amplifier might handle most of the work, but for a strong signal, the peaking amplifier kicks in more to help. ## What it does NOT cover - Does not cover power amplifiers that use only a single amplifier stage. - Does not cover power amplifiers where the bias inputs for the carrier and peaking amplifiers are fixed or adjusted independently without the inverse relationship described (carrier bias decreases as peaking bias increases). - Does not cover power amplifiers that split the RF input signal into more than two components (in-phase and quadrature phase). - Does not cover power amplifiers where the bias control signals are not derived from the magnitude of the RF input signal or the current drawn by the carrier amplifier. - Does not cover power amplifiers where the two amplified signals are not combined in additive phase. ## The clever bit The innovation lies in dynamically and inversely controlling the power (bias) to two separate amplifier stages based on the incoming signal's strength. This allows one amplifier to handle low-power signals efficiently, while the other steps in to provide additional power only when needed for stronger signals, preventing wasted energy. ## Real-world examples 1. Cellular base station power amplifiers 2. Smartphone radio frequency front-ends 3. Wi-Fi access point transmitters 4. Satellite communication transceivers 5. Broadcast radio and TV transmitters ## Why it matters Efficient power amplifiers are crucial for any device that transmits radio signals, like cell phones, Wi-Fi routers, and broadcast equipment. They consume a significant portion of a device's power, so improving their efficiency directly translates to longer battery life for mobile devices and reduced energy consumption for base stations. This patent describes a technique to achieve higher efficiency, especially when the signal strength varies, which is common in wireless communication. ## Frequently asked questions ### What does How a Radio Amplifier Saves Energy by Sharing Work cover? This patent describes a power amplifier design that dynamically adjusts the power supplied to two amplifier stages based on the strength of the incoming radio signal, making it more efficient. ### Who owns patent US 5757229? Motorola owns this patent, granted in 1998. ### When does this patent expire? This patent has expired and is now in the public domain — anyone can use the invention freely. ### What is patent US 5757229 cited by? This patent has been cited by 94 later patents that build on its ideas. ### What problem does this patent solve? Efficient power amplifiers are crucial for any device that transmits radio signals, like cell phones, Wi-Fi routers, and broadcast equipment. They consume a significant portion of a device's power, so improving their efficiency directly translates to longer battery life for mobile devices and reduced energy consumption for base stations. This patent describes a technique to achieve higher efficiency, especially when the signal strength varies, which is common in wireless communication. ### What does this patent NOT cover? Does not cover power amplifiers that use only a single amplifier stage. **Full plain-English explainer:** https://patentbrief.org/patent/us/5757229/bias-circuit-for-a-power-amplifier **Original patent:** https://patents.google.com/patent/US5757229 --- _Source: PatentBrief — https://patentbrief.org. Patent facts are from public records; the plain-English explanation is PatentBrief's._ ## Related patents Semantically similar inventions in the PatentBrief corpus: - [How Multi-Stage Power Amplifiers Save Battery Life in Wireless Devices](https://patentbrief.org/patent/us/8130043/multi-stage-power-amplifier-with-enhanced-efficiency) — This patent describes a clever way for electronic devices, like cell phones, to save battery power by using different amplifier circuits for strong and weak signals, making them more efficient. - [How an RF Amplifier Boosts Signal Power Efficiently](https://patentbrief.org/patent/us/6700444/n-way-rf-power-amplifier-with-increased-backoff-power-and-power-added-efficiency) — This patent describes an RF power amplifier design that uses a main amplifier and several auxiliary amplifiers to efficiently boost radio signals over a wide power range, especially useful in wireless communication basestations. - [How to Make Radio Amplifiers More Efficient](https://patentbrief.org/patent/us/8269555/efficient-linear-linc-power-amplifier) — This patent describes a method for tuning radio frequency power amplifiers to boost their efficiency and maintain a stable signal phase, especially when handling signals with changing loudness and direction. - [Making Radio Amplifiers More Efficient and Clear with Two Tricks](https://patentbrief.org/patent/us/10148229/pre-distortion-in-rf-path-in-combination-with-shaping-table-in-envelope-path-for) — This patent describes a smart way to make radio amplifiers, like those in cell phones, more efficient and produce a clearer signal by adjusting both the power supply and the input signal based on how strong the signal is. - [How Diodes Make Wireless Amplifiers Clearer](https://patentbrief.org/patent/us/8847689/stacked-amplifier-with-diode-based-biasing) — Qualcomm's patent describes a way to make electronic amplifiers, especially for wireless signals, produce clearer sound by using special diodes to adjust how much power they get based on the signal strength.